JPH069539A - Polyisocyanate composition having low viscosity and excellent low-temperature storage stability - Google Patents

Abstract

PURPOSE:To obtain a polyisocyanate composition having excellent low- temperature storage stability and giving a product having excellent physical properties by compounding various isomers of diphenylmethane diisocyanate at specific ratios. CONSTITUTION:The polyisocyanate composition is produced by compounding (A) 25-40wt.% of a polymethylenepolyphenylene polyisocyanate with (B) 60-75wt.% (in total) of 2,4'-diphenylmethane diisocyanate and 4,4'- diphenylmethane diisocyanate. In the component B, the ratio of (2,4'- diphenylmethane diisocyanate)/(4,4'-diphenylmethane diisocyanate) is 1/3 to 4/1, especially 1/3 to 2/1. The composition does not solidify at -10 deg.C to facilitate the storage and transportation at low temperature e.g. in the case of outdoor work in winter season or in cold district. The composition has excellent workability and gives a polyurethane foam, etc., having excellent properties.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a low-viscosity polyisocyanate composition having good low-temperature storage stability, and more particularly to a polyisocyanate composition containing diphenylmethane diisocyanate.

[0002]

2. Description of the Related Art Conventionally, polyisocyanates such as diphenylmethane diisocyanate have been widely used as raw materials for producing polyurethane products such as polyurethane foam, but especially when used or stored outdoors in winter or in cold regions, they are stored at low temperatures. Therefore, a property that does not easily crystallize, that is, storage stability at low temperature is required, and a low viscosity within a certain range is required in view of workability requirements such as mixing and transferring.

Generally, from the viewpoint of storage stability at low temperature, the lower the freezing point of the polyisocyanate is, the more preferable. In particular, it is required that the polyisocyanate does not solidify even at -10 ° C or lower. Further, if the viscosity is high, problems such as mixing and transfer may occur, so that the viscosity at 25 ° C. (measured by a rotary viscometer; the same applies hereinafter) is required to be 75 cps or less.

Conventionally, in order to improve storage stability at low temperatures, a method of reacting diphenylmethane diisocyanate containing 2,4'-isomer, 4,4'-isomer and the like with propylene glycol to form a prepolymer ( JP-A-53
No. 98942), a partial carbodiimidization method (JP-A-57-146747) and the like have been proposed, but these methods are disadvantageous in cost, increase viscosity, and have a small number of functional groups. There are problems such as difficulty in physical properties of the obtained product, and satisfactory results are not always obtained.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyisocyanate composition having good low temperature storage stability, low viscosity, and good physical properties of the product obtained.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted repeated studies to achieve the above object, and think that the above object can be achieved by blending various isomers of diphenylmethane diisocyanate well. Various studies were made on the composition.

4,4'-diphenylmethane diisocyanate (hereinafter referred to as "4,4'-MDI") has a melting point of 3
It is solid at room temperature at 9 ° C and must be melted during use.
Also, 2,4'-diphenylmethane diisocyanate (hereinafter referred to as "2,4'-MDI") has a melting point of 35 ° C.
It is a solid at room temperature and needs to be melted when used. The present inventor has made the above 4,4'-MDI and 2,4'-
It was found that, when MDI and HDI were uniformly mixed and blended in a molten state, the freezing point was lowered to about 15 ° C., for example, in a 50:50 blend, but at this freezing point, there was no practical meaning and further study was conducted. .

In the process, attention was paid to polymethylene polyphenylene polyisocyanate which is a by-product in the industrial production process of diphenylmethane diisocyanate. This polymethylene polyphenylene polyisocyanate is a liquid having a viscosity of 3000 to 10000 cps at room temperature, and is, for example, 4,4′-diaminodiphenylmethane or 2,4 ′ obtained by condensation reaction of aniline and formaldehyde.
By reacting a mixture of condensed anilines such as ′ -diaminodiphenylmethane and polyaminopolyphenylenepolymethylene with phosgene to convert the amino group into an isocyanate group, 4,4′-MDI or 2,4′-MDI is obtained.
Generated with.

The crude reaction mixture thus obtained (hereinafter referred to as "crude MDI") contains 4,4'-MDI as the main product and a small amount of less than 10% by weight of 2,4'-MDI and 2
It contains about 0 to 50% by weight of polymethylene polyphenylene polyisocyanate, and the viscosity at 25 ° C is about 50 cps, but there is a problem that its freezing point is high at about 0 to 5 ° C, and it is a crude product. It cannot be used as it is.

The present inventor has proposed that these 4,4'-MDI,
As a result of repeated research on a blend of 2,4′-MDI and polymethylene polyphenylene polyisocyanate, the above 4,4′-MDI and 2,4′-MDI were used in a specific ratio, and polymethylene was used. It has been found that, when blending with polyphenylene polyisocyanate in a specific ratio, the freezing point is significantly lowered, it does not actually solidify even at -10 ° C, and a low viscosity composition having a viscosity at 25 ° C of 75 cps or less can be obtained. It was The present invention has been completed based on this new finding.

That is, according to the present invention, (a) polymethylene polyphenylene polyisocyanate is 25 to 40% by weight, and (b) 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate are in total 60 to 75% by weight. %, And the ratio of 2,4'-diphenylmethane diisocyanate / 4,4'-diphenylmethane diisocyanate is in the range of 1/3 to 4/1, to provide a polyisocyanate composition.

The polymethylene polyphenylene polyisocyanate (hereinafter referred to as "polynuclear MDI") used in the present invention is a mixture of known compounds represented by the following chemical formula 1.

[0013]

[Chemical 1]

[In the formula, n represents an integer of 1 to 10. As described above, the polynuclear body MDI is industrially produced according to a conventional method described in, for example, Japanese Patent Publication No. 49-48318.
A mixture of condensed anilines such as 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane and polyaminopolyphenylenepolymethylene obtained by condensation reaction of aniline and formaldehyde is reacted with phosgene to convert the amino group into an isocyanate group. To 4,4'-MDI and 2,4'-MDI.

The polynuclear MDI thus obtained is usually
It is a high-viscosity liquid having a viscosity at 25 ° C. of about 3,000 to 10,000 cps, and the abundance ratio of the compound having n of 1 to 3 in the above chemical formula 1 is about 60 to 90% by weight, typically about 80.
Those having a weight percentage of about 10 can be particularly preferably used in the present invention.

In the present invention, the above polynuclear body MDI, 4, 4 '
Each of -MDI and 2,4'-MDI is advantageously used by isolating and purifying the product produced by the above method by a commonly used purification method such as rectification, but not limited to this method. Alternatively, those manufactured by other methods may be used.

In the present invention, the above polynuclear MDI is added to 2,4
Blend with'-MDI and 4,4'-MDI. At that time, with respect to the polynuclear body MDI 25 to 40% by weight, 2,
A total of 60 to 75% by weight of 4'-MDI and 4,4'-MDI are used.

Further, in the present invention, the use ratio of 2,4'-MDI and 4,4'-MDI is important, and 2,4'-MDI is used.
-MDI / 4,4'-MDI ratio is usually about 1/3 ~
The range of about 4/1 is preferable, the range of 1/3 to 2/1 is preferable, and the range of 2/5 to 2/1 is more preferable.

Such a specific 2,4'-MDI / 4,
2,4'-MDI and 4,4'-MDI in 4'-MDI ratio
And by blending this with polynuclear MDI at a specific ratio, the freezing point is -10 ° C or lower, and
It is possible to obtain a polyisocyanate composition having a low viscosity of 75 cps or less at 0 ° C., particularly 25 to 75 cps.

The polyisocyanate composition of the present invention is prepared by mixing the above-mentioned respective components in the above-mentioned predetermined proportions. At this time, the order of addition of the respective components and the mixing method are not particularly limited, and the respective components may be added. The mixture may be mixed in any order using an ordinary mixing device with slight heating if necessary.

The polyisocyanate composition of the present invention thus obtained is described, for example, in "Polyurethane Resin Handbook" (Keiji Iwata, Nikkan Kogyo Shimbun, September 2, 1987).
It can be advantageously used for the production of various products such as polyurethane foams, paints and adhesives according to the usual method described in (Published on 5th).

[0022]

According to the present invention, the following excellent effects can be achieved.

(1) The polyisocyanate composition of the present invention does not solidify even at −10 ° C., has extremely high storage stability at low temperatures, and can be easily stored and transferred at low temperatures outdoors in winter or in cold regions.

(2) The polyisocyanate composition of the present invention has a viscosity at 25 ° C. of 75 cps or less, particularly 25
Since it is ~ 75 cps, it is extremely excellent in workability. (3) Furthermore, since the polyisocyanate composition of the present invention has an appropriate viscosity range and also has an appropriate number of functional groups, it is excellent when the polyisocyanate composition of the present invention is used for producing a polyurethane foam or the like. A product with properties can be obtained.

[0025]

EXAMPLES The present invention will be described in more detail with reference to Reference Examples, Examples, Comparative Examples and Test Examples below. In these examples, “parts” and “%” refer to “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Reference Example 1 To 280 g (3 mol) of aniline, a 35% hydrochloric acid aqueous solution catalyst was added, and at 30 to 40 ° C., 164 g of a 37% formalin aqueous solution.
(2 mol) is gradually added and reacted at the same temperature for 2 hours. Furthermore, after heating at 90 ° C. for 3 hours to complete the condensation reaction, it is neutralized with an aqueous caustic soda solution. By filtration
By-produced sodium chloride was removed and water and unreacted raw materials were distilled off to obtain a mixture of condensed anilines.

2,4'-diphenylmethane diisocyanate (2,4'-MDI), 4 was obtained by reacting 352 g (3.6 mol) of phosgene with this mixture at 130 ° C. to convert the amino group into an isocyanate group. , 4 '
-Diphenylmethane diisocyanate (4,4'-MD
In addition to I),

[0028]

[Chemical 2]

[In the formula, n represents an integer of 1 to 10. ] The crude diphenylmethane diisocyanate containing the polymethylene polyphenylene polyisocyanate (polynuclear MDI) represented by this was obtained. This crude diphenylmethane diisocyanate is rectified to give 2,4'-MDI, 4,4'-M
DI (these are collectively referred to as "binuclear MDI") and polynuclear MDI were separated.

The obtained polynuclear MDI has a viscosity of 5000 cps at 25 ° C. and n in Chemical formula 2 is 1 to 3
The abundance ratio of the compound was 80% by weight based on the total weight of the polynuclear MDI.

Examples 1 to 5 , 2,4'-MDI, 4,4'-obtained in Reference Example 1 above
MDI and polynuclear MDI were blended in the proportions shown in Table 1 below to obtain the polyisocyanate composition of the present invention.

The viscosity of the obtained polyisocyanate composition was measured at 25 ° C. according to JIS K-7117 (a method for testing the viscosity of a liquid resin by a rotational viscometer).

The freezing point of the obtained polyisocyanate composition was measured as follows. That is, for one sample, the sample was divided into a plurality of test tubes, and each of these test tubes was immersed in a plurality of baths maintained at various temperatures in the range of 0 to -15 ° C for one month. Since a polyisocyanate composition containing a solid substance that can be visually observed has a problem in practical use, the temperature of the bath where the visually observable precipitation of the solid substance was observed after the immersion period was defined as the freezing point. This measurement was similarly performed on other samples.

Samples in which no crystallization was observed even after one month at -15 ° C had a freezing point below -15 ° C (<-15 ° C).

The results are also shown in Table 1.

[0036]

[Table 1]

As is clear from Table 1 above, the polyisocyanate composition of the present invention has a viscosity at 25 ° C. of 25.
It is in the range of ˜75 cps and has a very low freezing point of less than −15 ° C., indicating that the low temperature storage stability is high.

Comparative Examples 1 to 3 , 2,4'-MDI and 4,4'-obtained in Reference Example 1 above
MDI and polynuclear MDI were blended in the proportions shown in Table 2 below to obtain a comparative polyisocyanate composition.

The viscosity and freezing point of the obtained polyisocyanate composition were measured in the same manner as in Examples 1-5.

The results are also shown in Table 2.

[0041]

[Table 2]

As is clear from Table 2 above, multinuclear MD
It can be seen that when the amount of I used exceeds 40% by weight, the freezing point is low, but the viscosity at 25 ° C. far exceeds 75 cps.

The amount of polynuclear MDI used is 25-4.
Even within the range of 0% by weight, 2,4'-MDI / 4,
It can be seen that when the ratio of 4'-MDI is out of the range of 1/3 to 4/1, the viscosity is low, but the freezing point is high at -5 ° C and the low temperature storage stability is poor.

Claims (2)

[Claims] 1. (a) 25 to 40% by weight of polymethylene polyphenylene polyisocyanate and (b) 2,4 '.
A total of 60 to 75% by weight of diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, and the ratio of 2,4'-diphenylmethane diisocyanate / 4,4'-diphenylmethane diisocyanate is in the range of 1/3 to 4/1. A polyisocyanate composition comprising: 2. The polyisocyanate composition according to claim 1, wherein the ratio of 2,4′-diphenylmethane diisocyanate / 4,4′-diphenylmethane diisocyanate is in the range of 1/3 to 2/1. .