JPS58457B2 - Manufacturing method of low-density rigid urethane foam with less brittleness - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a low-density, rigid urethane foam that has excellent moldability, workability, mechanical properties, and heat insulation properties, and is less brittle. However, the foaming speed is fast, the initial strength is high even if the curing conditions after foaming are moderate, the compressive strength after curing is high, the dimensional stability is good at low temperatures, high temperatures, and high humidity, excellent abrasion resistance, and brittleness. The present invention relates to a method for producing a low-density rigid urethane foam that has a good feel and has excellent heat insulation properties.

Rigid urethane foam has better insulation properties than any other material, so it is widely used as an insulation material for electric refrigerators, freezers, cold boxes, etc.

Conventional hard urethane foam has a density of 0 due to its performance.
．． Although it is often used at around 0.030 g/cm3, there has recently been a strong demand for lower density in order to save resources, reduce weight, and lower prices.

Lowering the density of rigid urethane foam can be easily achieved by using a large amount of blowing agent, but lowering the density leads to a decrease in mechanical properties, a decrease in closed cell ratio,
This results in coarsening of the foam cells, deterioration of the foam tactility, increase in brittleness, deterioration in adhesion, deterioration in heat insulation, and deterioration in dimensional stability, and when conventional polyether polyols are used, the limit for lowering the density is 0. It is around 025g/cm3.

In addition, from the viewpoint of rationalizing the foaming process, shortening the time, and saving energy, there is a demand for lowering the foaming mold temperature, lowering the curing temperature, shortening the curing time, and increasing the initial strength.

In order to meet these demands, the terminal hydroxyl group of the polyether polyol using sucrose as one component of the initiator 5 has been made primary to increase the reactivity, and the reaction rate has been increased by changing the type and amount of the blowing catalyst. Although various studies have been conducted to increase the size, the former method has poor compatibility with foaming agents such as Freon F-11 (trichloromonofluoromethane) and foam stabilizers, resulting in turbidity or turbidity of the resin premix. Precipitation occurs and freon F-11 is easily volatilized, resulting in coarsening of foam cells, increased brittleness, and decreased tactility.

On the other hand, in the latter case, it is difficult to maintain a balance between gelation and foaming of the foam, and operability, processability, and moldability in the foaming process often deteriorate.

The present inventors have conducted extensive studies on these problems, and as a result, have arrived at the present invention.

The present invention produces a low-density rigid urethane foam with excellent moldability, processability, mechanical properties, and heat insulation properties, and less brittleness, from polyether polyol, polyisocyanate, foaming catalyst, foaming agent, and foam stabilizer. The polyether polyol is obtained by reacting (A) a 6- to 8-functional alcohol with water or at least one active hydrogen compound having 2 to 4 active hydrogen atoms, and propylene oxide. Hydroxyl value 300-500mgKOH/
A polyether polyol (hereinafter abbreviated as polyol A) of g, at least one type of active hydrogen compound having 2 to 4 active hydrogen atoms (B), and ethylene oxide or propylene oxide and ethylene oxide are reacted. A polyether polyol (hereinafter abbreviated as polyol B) with a hydroxyl value of 450 to 800 to KOH/g and which has primary hydroxyl groups at the terminal ends thereof (hereinafter abbreviated as polyol B) is mixed with a polyether polyol having a weight ratio of A to B of 95:5 to 30:700. This method is characterized by using polyether polyols mixed in the same proportions.

Examples of the 6- to 8-functional alcohols used in the present invention include sorbitol, mannitol, inositol, sucrose, and trehalose.

Active hydrogen compounds having 2 to 4 active hydrogen atoms used in the present invention include propylene glycol, ethylene glycol, diethylene glycol, diethylene glycol, glycerin, diglycerin, trimethylolpropane, hexanetriol, hexylene glycol, and neopentyl glycol. , bisphenol A, pentaerythritol, monoethanolamine, jetanolamine, triethanolamine, ethylenediamine, propylene diamine, etc. are used.

For the polyol A used in the present invention, a 6- to 8-functional alcohol, water, and an active hydrogen compound having 2 to 4 active hydrogen atoms are mixed, and propylene oxide is reacted in the presence of a basic catalyst. It can be obtained by letting

6-8 functional alcohols and water, 2 active hydrogen atoms
The weight ratio with the active hydrogen compound having ~4 is 100:1
You can freely change the ratio from 100 to 100,
Preferably, a ratio of 100:3 or 100:50 is used.

The hydroxyl value of polyol A is 300 to 500 mgKOH/
g is used, and when the hydroxyl value is 300 to KOH/P or less,
The physical properties of the foam decreased, and the hydroxyl value decreased to 500mgKOH/
If it exceeds g, the brittleness worsens.

As described above, the polyol A used in the present invention is quite different in content from polyols used to produce ordinary rigid polyurethane foams.

That is, it is characterized by increasing the ratio of the amount of 6- to 8-functional functional alcohols to water or active hydrogen compound, increasing the average number of functional groups, and decreasing the hydroxyl value.

Polyol B used in the present invention has 2 active hydrogen atoms.
Reacting an active hydrogen compound having ~4 atoms with ethylene oxide in the presence of a basic catalyst, or reacting an active hydrogen compound having 2 to 4 active hydrogen atoms with propylene oxide, and then reacting ethylene oxide. It can be obtained by

The amount of ethylene oxide used is at least 1 mole per active hydrogen atom.

The hydroxyl value of polyol B is 450 to 800 KOH/
f is used, and when the hydroxyl value is 450 to KOH/7 or less,
Form properties such as dimensional stability and compressive strength are poor, and 80
If it is 0 mgKOH/g or more, the viscosity of the polyol becomes high, the hydroxyl group of the mixed polyol becomes high, the amount of isocyanate used increases, and the cost of the foam increases, which is not a good idea.

The polyether polyol used in the present invention is a mixture of polyol A and polyol B at a weight ratio of A to B of 95:5 to 30:700.

Polyol A alone cannot produce a low-density, rigid urethane foam with excellent moldability, workability, mechanical properties, and heat insulation properties and low brittleness, which is the object of the present invention.

In other words, in an attempt to improve mechanical properties and dimensional stability, increasing the ratio of 6- to 8-functional polyhydric alcohols to water or active hydrogen compounds, or increasing the hydroxyl value of polyols may lead to brittleness. The cell properties and texture of the foam deteriorate, and the adhesion, moldability, closed cell ratio, heat insulation and processability deteriorate.

On the other hand, if the ratio of the 6- to 8-functional polyhydric alcohols to water or the active hydrogen compound used or the hydroxyl value of the polyol is reduced, the mechanical properties and dimensional stability will deteriorate.

If polyol B is used alone, the mechanical properties and dimensional stability will be extremely poor, making it unusable.

In this way, polyol A or polyol B alone,
A foam with excellent moldability, processability, physical properties, brittleness, and heat insulation properties as in the present invention cannot be obtained.

However, polyol A and polyol B designed according to the present invention have a weight ratio A/B of 9515.
When used in the range of 30/70, moldability,
It is possible to manufacture foams with well-balanced processability and foam properties.

By using the polyether polyol of the present invention,
The reason for the change in form, which has the above-mentioned excellent properties, is not clear, but the resin premix, excluding the polyisocyanate, maintains compatibility due to polyol A, which does not contain any ethylene oxide, and foams. The separation of the agent (trichloromonofluoromethane) is suppressed, and the viscosity is reduced by polyol B, thereby improving operability.

In the first stage of foaming, the reduced viscosity resin premix is efficiently mixed with the polyisocyanate, contributing to uniform foam formation, and polyol B and polyisocyanate react to create the foam skeleton. Because its skeleton is based on a low-functionality polyol, it has flexibility and contributes to foam elongation, liquid flowability, and foam regulation, and allows for reaction while maintaining uniform density and cell diameter. As the process progresses, the heat accumulated inside the foam causes polyol A to
It is thought that this promotes the second stage reaction between the polyisocyanate and the polyisocyanate, thickens the foam, and forms an even stronger foam.

Low density rigid urethane foams according to the invention can be produced by methods known to those of ordinary skill in the art by using the polyether polyols of the invention.

That is, a foam can be easily produced by mixing a polyether polyol, a polyisocyanate, a foaming catalyst, a foam stabilizer, and a foaming agent.

As the polyisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene 5-diisocyanate, crude tolylene diisocyanate, crude diphenylmethane diisocyanate, etc. are used.

As the foaming catalyst, tertiary amine compounds and organic tin compounds are used.

As the blowing agent, trichloromonofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane, monochlorodifluoromethane, water, methylene chloride, etc. are used.

The present invention will be explained below with reference to Examples, but the present invention is not limited thereto.

Reference example 1 21(7) In a pressure-resistant container, 408 g of sucrose and 20.4 g of water
After charging 3.7 g of potash and raising the internal temperature to 110°C, propylene oxide (hereinafter abbreviated as PO) was added.
1015 g was gradually charged so that the internal pressure did not exceed 4 kg/cm2.

After removing unreacted monomers, the internal temperature was raised to 80° C., and a 10% solution of phosphoric acid was added in an amount equivalent to the amount of potassium, and after reacting for 1 hour, dehydration and drying were performed.

Next, filtration is performed using a pre-coated filter, and 1
437g of product was obtained.

Product hydroxyl value is 416mgKOH/7, viscosity is 320
00 centipoise (25°C).

This is called polyol A-1.

Reference Examples 2 to 5 Polyols shown in Table 1 were synthesized in the same manner as in Reference Example 1.

Reference Example 6 By the same operation as in Reference Example 1, 698 g of glycerin and 1000 g of ethylene oxide (hereinafter abbreviated as EO) were reacted to give a hydroxyl value of 736 to KOH/g and a viscosity of 380.
I got a centipoise (25℃) product.

This is referred to as polyol B-1. Reference Example 7 Similarly to Reference Example 6, ethylenediamine 296P was added with PO.
700 g was reacted and then 705 g of EO was reacted.

The obtained product has a hydroxyl value of 633FQKOH/g and a viscosity of 2.
It was 300 centipoise.

This will be referred to as polyol B-2.

Reference Examples 8 to 14 Polyols shown in Table 2 were synthesized in the same manner as in Reference Example 6.

Example 1 Polyol A-180 parts, Polyol B-120 parts, Silicon L-5420 (Nippon Unicar product) 1.5 parts, water 1
0 parts, Freon F-11 (Mitsui Fluorochemical product) 43
part, Dabcor 33LV (mixture of triethylenediamine and diglopylene glycol in a ratio of 1:2) 1
．． 2 parts and dimethylethanolamine (hereinafter referred to as DMEA)
and 1.2 parts of TDI-TR.
C (Mitsui Toatsu crude tolylene diincyanate) and 110 parts of the mixture, stirred well for 5 seconds, and then poured into a cedar bowl (
17CrrL×17CIr1. ×17CIrL).

Rising time due to foaming (initiation time)
was 15 seconds, and the time for the foam surface to become tack-free (tack-free time) was 93 seconds.

After aging this foam overnight at room temperature, physical property tests were conducted.

The physical property test method is as follows.

(1) Density according to ASTM D-1622-59T.

, (2) Compressive strength according to ASTM D-1621-59T.

(3) Dimensional stability A 50 mm x 50 mm x 50 mm foam sample was left to stand under the conditions listed in the table, and its length was measured before being left to stand.

The rate of change in length after being left was determined.

(4) Taper set abrasion test Using a taper set abrasion tester manufactured by Toyo Seiki, the foam sample was rotated 20 times using a wheel with a load of 250 g to determine the weight loss (ΔW) of the sample.

It was calculated using the following formula.

Fragility Index=25/ΔW (5) Touch of Foam A foam sample was scratched with a finger, and the fragility of the foam at that time was observed.

(6) Cell characteristics The shape, uniformity, number of cells, cell membrane, etc. of the form cells were observed and evaluated with the naked eye and with an optical microscope.

The physical properties of the foam are as follows.

Comparative Example 1 A typical brand of Mitsui Polyether SU-4 used in conventional low-density foam was prepared in the same manner as in Example 1.
Foaming was performed using 50M (Mitsui Toatsu Chemicals).

The physical properties of the foam are as follows.

Comparative Examples 2 to 3 A foam was formed in the same manner as in Example 1 using polyol A-3 and polyol B-6.

Table 3 shows the evaluation of the foam.

Examples 2-3 To demonstrate the limiting amount of polyol B of the present invention, polyol A-3 and polyol B-6 were each given at 9515.3
A foam was formed in the same manner as in Example 1 using polyols mixed at a ratio of 0/70.

Table 3 shows the evaluation of the foam.

As can be seen from Table 3, polyol A alone does not improve the foam tactility based on the coarseness and non-uniformity of the foam cells.
The closed cell ratio and brittleness decreased significantly, and polyol B
In this case, the mechanical properties and dimensional stability are significantly reduced.

When polyol B exceeds 5% of the total polyol, brittleness, cell properties, and feel are improved; when it exceeds 70%, mechanical properties and dimensional stability decrease.

Example 4 Polyol A-180 parts, Polyol B-220 parts, water LO part, Dove-7-33LV1.3 parts, DMEAl, 3
Part, Silicon L-54201-5 part, Freon F-11
Panel foaming was performed using 42.3 parts of TRC and 105.9 parts of TRC.

The panel is 5 mm thick, 500 mm long and 500 m wide.
A wooden frame with a thickness of 30 mm was placed inside two aluminum plates of 30 mm in size.

After thoroughly stirring the foaming ingredients, they were poured into an aluminum panel kept at 30°C, and after foaming was completed, they were placed in an open oven at 50°C for 10 minutes to harden, then cured at 25°C for 2 hours, and then immediately Dimensional stability was tested.

The physical properties of the foam are as follows.

Comparative Examples 4 to 5 Panel foaming was performed in the same manner as in Example 4 using polyol A-3 and polyol B-8.

Table 4 shows the evaluation of the foam.

Examples 5 to 6 Polyol B of the present invention (7) In order to demonstrate the IIsJI limit, Example 4 was prepared using a polyol prepared by mixing polyol A-3 and polyol B-8 in a ratio of 9515.30/70. It was made into a form by the same operation as above.

Table 4 shows the evaluation of the foam.

As can be seen from Table 4, when polyol A-3 is used alone, the density ratio is large and the density distribution is wide.
Dimensional stability appears to decrease at lower densities within the foam.

In addition, non-uniformity and roughness of the form cells lower the closed cell ratio and deteriorate the thermal conductivity.

When polyol B-8 is used alone, the density ratio, cell properties, tactile feel, etc. are good, but the dimensional stability is extremely poor because the foam skeleton is weak.

Mixing ratio of polyol A-3 and polyol B-8 is 9515
~1 at 30/70, moderately balanced.

Examples 7 to 11 Panel foaming was performed in the same manner as in Example 4 using the polyether polyols listed in the table.

The foaming results are shown in Table 5.

Comparative Example 6 Panel foaming was performed in the same manner as in Example 4 using polyether BDE435 (manufactured by Union Carbide).

The foaming results are shown in Table 5.

As can be seen from Table 5, in Comparative Example 6, polyether polyol BDE435 in which propylene oxide and ethylene oxide were added using sucrose as an initiator was used. There is a problem with compatibility with 11th grade,
Also, since it does not mix well with TRC, when the density is reduced, the foam cells become rough and the texture is not good.

It has a low closed cell ratio and is not suitable as a heat insulating material.

On the other hand, by using the polyether of the present invention, a foam with good balance in moldability, processability, foam appearance, and physical properties can be obtained.

Claims (1)

[Claims] 1. For producing a low-density rigid urethane foam with excellent moldability, processability, mechanical properties, and heat insulation properties and less brittleness from polyether polyol, polyincyanate, foaming catalyst, foaming agent, and foam stabilizer. , a polyether polyol with a hydroxyl value of 300 obtained by reacting (A) a 6- to 8-functional alcohol, water or at least one active hydrogen compound having 2 to 4 active hydrogen atoms, and propylene oxide; ~500mgKOH/g polyether polyol and (B) 2 to 4 active hydrogen atoms
A hydroxyl value of 450 to 800 mgKOH, which is obtained by reacting at least one type of active hydrogen compound with ethylene oxide, or propylene oxide and ethylene oxide, and has a hydroxyl group whose terminal is primarily primary.
/g of polyether polyol, and the weight ratio A to B is 9.
A method characterized in that the components are mixed at a ratio of 5:5 to 30:700.