JPS6023133B2 - Manufacturing method of semi-rigid/hard resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Objective of the Invention) The present invention aims at reducing the amount of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as MDI) to a urethane prepolymer having an extremely low percentage of terminal NCO groups. This invention relates to a method for manufacturing semi-rigid/hard resin foams that allows the physical properties of impregnated foams to be freely adjusted by adjusting them on-site.

(Subject technology) Conventional urethane prepolymers are made by reacting tolylene diisocyanate (hereinafter abbreviated as TDI) and polyol, and based on this, the percentage of terminal NCO groups of this prepolymer is adjusted according to the desired physical properties. The desired physical properties of the final product were determined in advance at the polymerization stage.

That is, if the NCO group % is increased, the hardness and impact absorption properties are increased, and if the NCO group % is decreased, these are decreased and the cushioning properties and elongation are increased. However, changing the percentage of terminal NCO groups in this brepolymer is usually only possible by going further back in the manufacturing process and at the basic chemical plant that produces the raw materials.

Moreover, since basic chemical factories are mass-produced, there is no flexibility in manufacturing products with various NCO group percentages according to the preferences of end users. Therefore, it is very difficult for users to manufacture a resin-impregnated foam having a desired hardness, and it is usually not possible to manufacture a resin-impregnated foam having a certain hardness. Even if the hardness was to be changed by force, the amount of impregnation in the foam had to be adjusted carefully, and unnecessary solvents were used, resulting in a tedious and inefficient process. Furthermore, as the NCO group content increases, free TDI naturally increases, and according to environmental hygiene standards, drugs with TDI exceeding 1% are designated as specified chemical substances and are subject to special handling in terms of environmental hygiene. Become. Therefore, the use of TDI groups above a certain level may cause some problems. (Structure of the Invention) The present invention is intended to eliminate the above-mentioned drawbacks, and is made by reducing the amount of TDI and reacting it with a polyol so that the percentage of NCO groups is extremely low, and by using only one type of urethane prepolymer. is made in advance at a basic chemical factory.

After that, at the site of use such as molding processing, 4,4-diphenylmethane diisocyanate (hereinafter abbreviated as MDI)
After reaction and curing, the desired amount is mixed to achieve the desired physical properties, impregnated into a soft resin foam, and then compressed and cured in a hot press mold. MDI is a chemical that has come into use relatively recently, and is used especially when cold curing is required when manufacturing urethane foam, or as an adhesive for shoe making or laminating urethane foam strips with cloth, etc. It is just something that has been done.

Urethane prepo IJmer with extremely few NCO groups is a common product and is freely available.

To this, MD may be mixed to obtain the desired hardness. Urethane prepolymers with very few NCO groups are easily miscible with MDI. Furthermore, since MDI has higher reactivity than TDI, when this mixed liquid is used, productivity is improved compared to when a pre-volume using only TDI is used. In addition, even if you try to make a urethane prepolymer using only MDI and polyol, even if the two react and even a slight urethane bond occurs, the reaction will instantly become extremely viscous, making it unusable. It is not made at all.

In this application, such a problem does not occur even if MDI is mixed with a normal urethane prepolymer made by reacting TDI with a polyol. To describe an example using the present application, a molded article made by hot pressing is prepared by mixing MDI in the aforementioned urethane prepolymer in a proportion depending on the desired physical properties after curing, and impregnation using methylene chloride as a solvent. make a liquid,
A soft urethane foam plate is impregnated with this, and the excess impregnating liquid is squeezed out using a roller, etc., and the methylene chloride is removed by overflowing slightly. The urethane prepolyfoam is thinly and uniformly adhered to the inner wall of each cell of the urethane foam by volatilizing the Ride. Next, it is placed in a hot press mold and compressed while heating with steam, and the reaction occurs immediately and the molding is completed. Conventionally, it took more than 10 minutes to make a molded product using a normal foaming method, but according to the present invention, it only takes about 2 minutes, making the production speed extremely fast. However, even very thin parts and details can be easily molded. Furthermore, if you want to decorate the surface with a decorative skin, cover the surface with the skin during pressing and press it down to create an integral molding without using adhesive. (Function of the Invention) Table 1 shows the change in hardness depending on the ratio of the amount of MDI to the urethane prepolymer of the impregnating agent for semi-rigid resin foam of the present application.

On the horizontal hoe, the left end is MDIIOO%, the right end is 100% urethane prepolymer, and the center shows 1:1, ie, equal mixing. The hard axis shows the scale of hardness according to ASKER-F Type. The figure shows that the greater the amount of MDI mixed, the greater the hardness. Figure 2 shows the change in the tensile strength of the impregnated foam due to the difference in the ratio of the constituent amounts of the urethane prepolymer and MDI as the impregnating agent, and the horizontal axis is the same as in Figure 1. Made of 100% polymer, the hard shaft has a tensile strength of k9'
It is shown in units of land.

Figure 3 is the same (urethane prepolymer and MDI impregnating agent)
As for the horizontal axis of the impregnated foam due to the difference in the ratio of the constituent amounts, as before, the left end is MDIIOO%, the fabric end is 100% urethane prepolymer, and the hard axis represents the elongation in %.

According to the diagram, the curve is almost straight with a diagonal line and about 2
It has grown from 0% to 95% in the upper right corner. This figure shows that MDI
It shows that as the amount of admixture increases, the brittleness increases. FIG. 4 also shows the impact resilience change of the impregnated foam due to the difference in the ratio of the urethane prepolymer and MDI constituting the impregnating agent.

Similarly, the left end of the horizontal axis shows MDIIOO%, the right end shows 100% urethane prepolymer, the center shows 1:1, and Kanto shows impact resilience in %. This curve shows that the left end is low and the upward slope gradually becomes steeper, and as the MDI decreases, the rebound resilience increases. That is, generally speaking, the larger the amount of MDI, the harder and more brittle the material becomes, and the larger the amount of urethane polymer, the more flexible and fluffy the material becomes. The tensile strength occurs in the area where hardness and elongation exactly match in a 1:1 ratio. This has the advantage that products meeting the required physical properties can be manufactured on-site by easily changing the mixture of chemicals. (Effects of the Invention) The present invention reduces the amount of TDI so that the percentage of NCO groups is extremely low.
A urethane prepolymer is made by reacting with
Since MDI is mixed and impregnated into a resin foam at various locations where it is used, adjusting the amount depending on the desired physical properties, it is possible to freely change the physical properties such as hardness of the resin foam molded product. .

Therefore, resin foam molded articles with various physical properties can be obtained by preparing only one type of urethane prepolymer without requiring each type. Furthermore, the reactive group NCO
is caused by MDI from TDI,
Improving productivity and improving environmental conditions are also significant.

[Brief explanation of the drawing]

Figure 1 is a diagram of changes in hardness of the impregnated foam due to differences in composition of the urethane prepolymer and MDI mixture, Figure 2 is a diagram of changes in strength, Figure 3 is a diagram of changes in elongation, and Figure 4 is a diagram of impact resilience. be. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Reduce the amount of tridiisocyanate in advance to keep the NCO group % extremely low, and mix 4,4'-diphenylmethane diisocyanate at an appropriate mixing ratio with the urethane prepolymer produced by reacting with polyol immediately before molding. A method for producing a semi-rigid/hard resin foam having desired physical properties by mixing and impregnating it into a soft resin foam and heating it in a mold.