JPS6236420A - Production of urethane foam - Google Patents

Abstract

PURPOSE:To obtain a good foam excellent in elasticity and hardness, by foaming polyether polyol containing crude tolylene diiscocyanate, a polymer polyol, water, an amine catalyst and a silicone oil. CONSTITUTION:Crude tolylene diisocyanate of the formula (wherein n=0-2, a mixtue), water, an amine catalyst and a silicone oil are added to 100pts.wt. polyether polyol having MW>=1,000 and an ethylene oxide content of 5-80wt%. If necessary, a tin catalyst, a filler, pigment, etc., are further added, and the mixture is further mixed with agitation and foamed. Because of good compatibility of said polyether polyol with the crude tolylene diisocyanate, they can be uniformly mixed with other components and formed. Therefore, the reaction of forming a urethane foam can proceed smoothly and uniformly so that an urethane foam of food properties may be obtained though the reactivity of the crude tolylene diisocyanate is generally excessively high.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing a urethane foam, and particularly to a method for producing a urethane foam using crude MDI as an incyanate component.

[Technical background of the invention]

Urethane foam is widely used as various cushioning materials, bedding materials, and industrial materials. These urethane foams are manufactured by a continuous production method or a mold foaming method, and either foaming method employs the following basic foaming operation.

That is, the following components are mixed in a predetermined ratio and reacted to cause a urethane bond growth reaction, a foaming reaction, and a crosslinking reaction to occur simultaneously.

(1) Polyols such as polyether polyols and polyester polyols (2)) Organic incyanates such as lylene diisocyanate, diphenylmethane diisocyanate, and crude MDI (3) Water (blowing agent, crosslinking agent) (4) Amine catalyst (foaming Reaction catalyst) - (5) Tin-based catalyst (crosslinking reaction catalyst) (6) Silicone oil (foam stabilizer) (7) Optional components such as pigments and fillers The above polyols and organic isocyanates are expressed by the following formula: The urethane bond growth reaction shown is carried out.

0H-R-OH+ 0CN-R'-NCO\,. . −
□・-N. .

On the other hand, a foaming reaction is carried out using an organic isocyanate and water according to the following formula.

R-NGO+H,01→R-NH,+co2↑ The amine produced by the above foaming reaction reacts with the organic isocyanate as shown below to form a urea bond.

R-NH2+ R-NCO Further, the crosslinking reaction is carried out by the reaction between the above-mentioned urea bond and the terminal NCO group of the urethane growing chain formed by the above-mentioned growth reaction as follows.

In the production of urethane foam, it is extremely important to balance the foaming reaction and crosslinking reaction, and by controlling this balance, the open or closed state of the cells is controlled. Therefore, in the production of urethane foam, it is necessary to select conditions such that the above reactions proceed uniformly and smoothly and each reaction is suitably balanced.

Furthermore, an amine catalyst that promotes the foaming reaction and a tin catalyst that promotes the crosslinking reaction are both considered to be essential components in producing urethane foam.

[Conventional technology]

The urethane foams produced as described above are roughly divided into two types: soft foams and hard foams. Among these, when producing soft foams (including semi-rigid foams), tolylene diisocyanate (hereinafter abbreviated as TDI) is generally used as an incyanate component.

On the other hand, diphenylmethane 4,4'-diisocyanate represented by the following formula is solid at room temperature.

Mixing is difficult because it only melts at about 40℃, and TD
It is less common than I.

Moreover, crude MDI represented by the following formula has extremely high reactivity and is difficult to foam uniformly, so it is not used alone.

(However, it is a mixture of n = 0 to 2, and the mixing ratio is random.) However, in order to improve the physical properties such as hardness and flame retardance of the obtained urethane foam, crude MDI is mixed with 100 parts by weight of urethane foam. It is usually mixed at a maximum ratio of 50 parts by weight or less with respect to TDI, and may be used in combination.

[Problem that the invention seeks to solve]

TDI, which has been conventionally used as an incyanate component, is highly toxic and highly volatile, causing many problems in the working environment, such as damaging the eyes and tracheal branches.

On the other hand, crude MDI is less toxic and less volatile than TDI, so it is extremely desirable from the viewpoint of maintaining a safe working environment. However, if crude MDI is used alone as the isocyanate component and is mixed and stirred with other ordinary polyurethane foam raw materials and foamed, the resulting urethane foam will foam, but there is a problem in that the resulting urethane foam will shrink significantly over time. be. This means that the formed cell structure is a closed cell, and the reason is considered as follows.

That is, it is presumed that this is because the balance between the foaming reaction and the crosslinking reaction described above was lost, and the crosslinking reaction proceeded too quickly, causing the matrix resin to harden before the foaming gas could escape. In addition, crude MDI has poor compatibility with commonly used polyol components and does not mix uniformly.For this reason, the three types of reactions mentioned above during the formation of urethane foam do not proceed smoothly and the balance of one reaction is disturbed. This is thought to be a contributing factor.

This tendency is the same when crude MDI is mixed with TDI, and if the mixing ratio of crude MDI exceeds 50% by weight, the resulting urethane foam will shrink. Furthermore, even when the mixing ratio is 50% by weight or less, it may be necessary to destroy the membrane between the closed cells by physically rolling the obtained urethane foam, such as softening it with a roll or the like.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned point (1), and provides a method for producing a soft or semi-rigid polyurethane foam having excellent physical properties such as elasticity and hardness by using crude MDI alone as an incyanate component. This is what we provide.

[Summary of the invention]

The present invention uses crude MDI alone as an isocyanate component by selecting a polyether polyol with an ethylene oxide content of 10 to 80% by weight and a molecular weight of 1000 or more as a polyol component, and adding a polymer polyol. This makes it possible to obtain a soft to semi-hard urethane foam that hardly shrinks over time by foaming.

Since the polyether polyol selected in the present invention has good compatibility with crude MDI, it is uniformly mixed when both are mixed together with other raw material components and foamed. As a result, the above-mentioned urethane foam forming reaction proceeds smoothly and uniformly, and it is thought that a urethane foam with good foaming properties can be obtained, even though the reactivity of crude MDI is generally too high.

In addition, in the present invention, the polymer polyol added to the polyether polyol refers to a resin such as acrylic or vinyl chloride when synthesizing a polyol with a desired molecular weight by addition polymerizing ethylene oxide or the like to a starting material such as glycerin. is introduced into the polyol molecule. By adding this polymer polyol, shrinkage of the obtained urethane foam over time is significantly prevented. This is considered to be because the resin component introduced into the molecule prevents shrinkage by some action. The amount of this polymer polyol added is not particularly limited, but a suitable range is 20 to 85 parts by weight per 100 parts by weight of the polyether polyol.

In addition, in the present invention, it has become clear that a urethane foam having the desired physical properties can be produced without adding a tin catalyst, which was considered to be an essential component for promoting the crosslinking reaction. This seems to be because crude MDI has high reactivity, so the crosslinking reaction proceeds even in the absence of a tin catalyst.

However, there is no problem in adding a tin catalyst if necessary.

The present invention can be applied to both continuous foaming and mold foaming.

[Embodiments of the invention]

The present invention will be explained in detail below.

Example 1.2 Using the formulation shown in Table 1 below, these raw materials were mixed and foamed by a one-shot method to produce urethane foam.

Further, as a comparative example, a urethane foam was produced in the same manner without adding a polymer polyol and using polypropylene ether polyol, which has been conventionally used as a polyol.

When samples of the urethane foams obtained in Examples and Comparative Examples were prepared and their density and hardness were examined, the results shown in Table 1 were obtained.

〔Effect of the invention〕

As described in detail above, according to the present invention, urethane foam can be manufactured using only crude MDI as the incyanate component, so the work is easier compared to the conventional manufacturing method that uses highly toxic TI)I as the inocyanate. safety can be improved.

In addition, the conventional manufacturing method using TDI required fine adjustment of the formulation to increase the hardness of the foam, but the present invention using crude MDI does not require such fine adjustment of the formulation. A relatively hard urethane foam can be obtained.

As described above, the present invention provides remarkable effects that have not been achieved conventionally.

Claims (1)

[Claims] For 100 parts by weight of a polyether polyol with an ethylene oxide content of 5 to 80% by weight and a molecular weight of 1000 or more, crude MDI represented by the following formula: ▲A mathematical formula, chemical formula, table, etc. (However, it is a mixture of n = 0 to 2, and the mixing ratio is random.) Add the polymer polyol, water, amine catalyst, and silicone oil, and add tin catalyst, filler, pigment, etc. as necessary. A method for producing urethane foam, which comprises adding, mixing, stirring, and foaming.