JPS581130B2 - How to use the temporary foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing low density rigid urethane foam.

Rigid urethane foam is often used in electric refrigerators, freezers, coolers, etc. due to its excellent insulation properties.

Previously, due to quality constraints, the foam density was 0.030g/
A material with a density of about 3 cm was used, but there is a strong demand for a lower density in order to save resources, save energy, lower prices, and reduce weight.

Lowering the density of rigid urethane foam can be easily achieved by increasing the amount of blowing agent. This causes deterioration in dimensional stability, decrease in closed cell ratio, deterioration in heat insulation, and deterioration in brittleness, and it is said that the current limit is a density of 0.025 g/cm3.

On the other hand, from the point of view of rationalizing the production of rigid urethane foam, it is desired to lower the foaming mold temperature, ease the curing conditions, and shorten the mold cycle.

For this purpose, if a large amount of foaming catalyst is used, it will be difficult to maintain a balance between gelation and foaming, and foams with uniform cell diameters may not be obtained, or from the start of the reaction,
The interval until the apparent completion of the reaction is often shortened, resulting in poor liquid flow, operability, and processability. Although attempts have been made to use reactive polyols, the compatibility with Freon F-11 (trichloromonofluoromethane) as a blowing agent, foam stabilizers, etc. decreases, and the stability of the resin premix deteriorates. Not only does this impair operability, but it also makes it impossible to obtain high-quality foam.

The present inventor has conducted various studies regarding these problems and has arrived at the present invention.

The present invention uses (A) as a polyether polyol in producing a low-density rigid urethane foam with excellent moldability, processability, and mechanical properties and low brittleness from a polyether polyol, a polyisocyanate, and a foaming aid. A polyether polyol (hereinafter abbreviated as polyol-A) with a hydroxyl value of 400 to 600 mgKOH/g obtained by reacting sucrose and an active hydrogen compound having 2 to 4 active hydrogen atoms with propylene oxide, B) A polyether polyol with a hydroxyl value of 400 to 800 mgKOH/g, which has a primary hydroxyl group at the end, obtained using an active hydrogen compound having 2 to 4 active hydrogen atoms as an initiator, and a polyisocyanate are OH This method is characterized in that the weight ratio of polyether polyol containing urethane bonds in the /NCO moiety (hereinafter abbreviated as polyol B) is used.

By using the polyether polyol of the present invention,
Although the reaction mechanism and structural characteristics of a low-density rigid urethane foam with excellent moldability, workability, and mechanical properties and low brittleness are not clear, as the first step of the reaction,
Polyol-B and polyisocyanate react to create a foam skeleton, and because the skeleton was obtained by the reaction between a low-functionality polyol and polyisocyanate, it has flexibility, and the foam rises and This facilitates liquid flow and makes it easier to create a low-density foam with a narrow density distribution.Then, the heat accumulated in the foam causes a second stage reaction to occur between polyol-A and polyisocyanate, creating an even stronger foam. It is thought to form a

In other words, polyol A mainly contributes to the stability, dimensional stability, and mechanical properties of the resin premix, and polyol B contributes to low-temperature foaming, relaxing curing conditions, shortening mold cycles, and developing initial strength. And polyol-
It is believed that the synergistic effect of A and polyol-B improves the uniformity, feel, brittleness, closed cell ratio, and heat insulation properties of the foam cells.

Polyol-A used in the present invention can be obtained by reacting sucrose and an active hydrogen compound having 2 to 4 active hydrogen atoms with propylene oxide in the presence of a basic catalyst.

The active hydrogen compounds having 2 to 4 active hydrogen atoms used in the present invention include water; ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, trimethylolpropane,
, 1,1-trimethylolethane, 1,2,4-trihydroxybutane, 1,2,6-trihydroxyhexane, pentaerythritol, diglycerin, and other polyhydric alcohols; monoethanolamine, diethanolamine, triethanolamine , aminoalcohols such as aminophenol; diamines such as ethylenediamine, tetramethylenediamine, pentamethylenediamine, and the like.

The weight ratio of sucrose and active hydrogen compound is 100/2 to 1
00/100 is used, and the amount of the active hydrogen compound used varies depending on the type of active hydrogen compound and the desired hydroxyl value of the polyol.

The hydroxyl value of polyol-A is 400 to 600 mgKO
H/g is used, and if the hydroxyl value is less than 400,
Dimensional stability and mechanical properties deteriorated, and 600mgKOH/
If it is larger than g, the stability, brittleness, and cell properties of the resin premix will decrease.

Polyol-B used in the present invention is obtained using an active hydrogen compound having 2 to 4 active hydrogen atoms as an initiator, has a primary hydroxyl group at the end, and has a hydroxyl value of 400.
This is a polyether polyol containing urethane bonds in an OH/NCO ratio of polyether polyol (hereinafter abbreviated as polyol-C) of ~800 mgKOH/g and polyisocyanate.

Polyol-C can be obtained by reacting the above-mentioned active hydrogen compound with ethylene oxide in the presence of a basic catalyst, or by reacting propylene oxide and then reacting with ethylene oxide.

The amount of ethylene oxide used at this time is at least 1 mol or more per active hydrogen of the active hydrogen compound.

Polyol-B can be obtained by reacting polyisocyanate while dropping it into polyol-C, or by mixing polyol-C and polyisocyanate at a relatively low temperature and allowing them to react gradually.

The reaction depends on the type of polyol-C, but generally 3
It is carried out at a temperature of 0 to 100°C.

Completion of the reaction is determined by the presence or absence of unreacted NCO groups.

If the viscosity of the product of Rule B using polyol-C and polyisocyanate becomes high or there is a high risk of gelation,
The characteristics of polyol-B are lost.

The polyisocyanates used in the production of polyol-B include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and 1,5-naphthylene diisocyanate. diisocyanate, O-, m- or p-xylylene diisocyanate, tetramethylene diisocyanate, crude tolylene diisocyanate, crude diphenylmethane diisocyanate, and the like.

The polyether polyol used in the present invention cannot produce a low-density rigid urethane foam with excellent moldability, processability, mechanical properties, and heat insulation properties and low brittleness by using polyol-A alone.

In other words, in an attempt to improve the mechanical properties and dimensional stability of the foam, increasing the ratio of sucrose to active hydrogen compound or increasing the hydroxyl value of polyol-A worsens the brittleness of the foam. Cell properties and feel deteriorate, and adhesion, moldability, closed cell ratio, heat insulation properties, etc. decrease.

On the other hand, in an attempt to improve brittleness, foam cell properties, texture, etc., the ratio of sucrose to active hydrogen compound used, or the hydroxyl value of polyol-A, may be reduced, resulting in poor mechanical properties and dimensional stability. decreases.

Furthermore, when polyol-B is used alone, the mechanical properties and dimensional stability are poor and it cannot be used.

Thus, polyol-A or polyol-B alone cannot provide a foam with excellent moldability, processability, physical properties, brittleness, and heat insulation properties as in the present invention.

However, the moldability of polyol-A and polyol-B designed according to the present invention is determined by the weight ratio.
Producing foam with well-balanced processability, brittleness, feel, and foam cell properties When the various drawbacks mentioned in the case of polyol A alone are smaller than the table above, the same drawbacks as in the case of polyol B alone appear. Undesirable.

Rigid urethane foam can be manufactured by methods known to those skilled in the art.

As the polyisocyanate, those similar to those used in the production of polyol B are used.

As the foaming aid, a foaming catalyst, a foaming agent, and a foam stabilizer are used.

As the foaming catalyst, a tertiary amine compound, an organic tin compound, etc. are used, and as the foaming agent, water, trichloromonofluoromethane, cyclodifluoromethane, dichlorotetrafluoroethane, monochlorodifluoromethane, etc. are used.

As the foam stabilizer, silicone-based foam stabilizers having a polysiloxane skeleton and liquid paraffin-based foam stabilizers are used.

According to the invention, the foaming can be carried out by a one-step process, a prepolymer process or a semi-prepolymer process.

The foam obtained according to the present invention can be used in all fields in which hard urethane foam has been conventionally used, such as in the field of heat insulation and soundproofing of electric refrigerators, freezers, cold boxes, walls, doors, etc.

Next, the present invention will be explained with examples.

Reference Example-1 450 g of sucrose, 48 g of water, and 4.2 g of caustic potash were charged into a 2-liter pressure-resistant container, the internal temperature was brought to 110°C, and then 1148 g of propylene oxide (hereinafter abbreviated as PO) was charged at an internal pressure of 4 kg/ It was charged gradually so as not to exceed cm2.

After the reaction was completed, an 85% aqueous phosphoric acid solution was added in an equimolar amount to the caustic potash for neutralization.

After neutralization, filter through a pre-coated filter to obtain product 1622.
I got g.

The obtained product had a hydroxyl value of 450 mgKOH/g and a viscosity of 32,500 centipoise (25°C).

This is called polyol A-1.

Reference Example 2 In the same manner as Reference Example 1, 1880 g of polyether polyol was obtained using 390 g of sucrose, 210 g of glycerin, 4.2 g of caustic potash, and 1400 g of PO.

The obtained product had a hydroxyl value of 435 mgKOH/g and a viscosity of 8,400 CPS (25°C).

This is called polyol A-2.

Reference Examples 3 to 5 Polyether polyols shown in Table 1 were synthesized in the same manner as in Reference Example 1.

Reference Example-6 Ethylene oxide (hereinafter referred to as E) is added to propylene glycol.
600 g of polyol (hydroxyl value 607 mgKOH/g) obtained by adding TDI-/(
Mitsui Toatsu Chemicals Tolylene Diisocyanate (150 g) was placed in a glass reactor and reacted at room temperature under a nitrogen atmosphere, and then the internal temperature was raised to 60° C. and reacted for 3 hours.

The obtained polyol had a hydroxyl value of 378 mgKOH/g and a viscosity of 2120 cps (25°C).

This is called polyol B-1. Reference Examples-7 to -13 Polyol-B shown in Table-2 was produced in the same manner as in Reference Example-6.

However, C-1 is a polyol with a hydroxyl value of 736 mgKOH/g obtained by reacting glycerin with EO, and C-2 is a polyol with a hydroxyl value of 545 mgK obtained by reacting glycerin with EO.
Polyol C-3 of OH/g was obtained by reacting 533 g of pentaerythritol with 213 g of PO and then reacting with EO853.
Polyol C-4, which has a hydroxyl value of 554 mgKOH/g, is obtained by reacting triethanolamine with EO. Polyol C-5, which has a hydroxyl value of 679 mgKOH/g, is obtained by reacting ethylenediamine with EO. Polyol TDI-T with a value of 558 mgKOH/g
RC is Mitsui Toatsu Chemicals crude tolylene diisocyanate;
MDI-CR is Mitsui Toatsu Chemicals crude diphenylmethane diisocyanate.

Example-1 Polyol A-3 80 parts, Polyol B-120 parts,
1.0 part of water, 40 parts of Freon F-11 (Mitsui Fluorochemical product, trichloromonofluoromethane), Silicon L
-5420 (Japan Unicar product) 1.5 parts, Dabko 33
1.5 parts of LV (33% dipropylene glycol solution of triethylene diamine) and 1.5 parts of dimethylethanolamine (hereinafter abbreviated as DMEA) were mixed well in a 500 ml paper cup, and the TDI-TRC was dissolved in NCO/OH. =
1.05, stir vigorously for 5 seconds, and add 17
It was injected into a cardboard box measuring cm x 17 cm x 17 cm.

The time for foaming to rise (initiation time) is 14 seconds, and the time for the foam surface to become sticky (
The tack free time) was 116 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 Foam samples of 50 x 50 x 50 mm were left under the conditions listed in the table, and the rate of change in length after standing was determined relative to the length before standing.

(4) Taber set abrasion test A foam sample was rotated 20 times with a wheel with a load of 250 g using a Taber set abrasion tester manufactured by Toyo Seiki, and the weight loss (ΔW) of the sample was determined and calculated using the following formula.

Fragility Index -25/ΔW (5) A foam sample of the foam was scratched with a finger, and the fragility of the foam was observed.

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

The foam physical properties are as follows.

Density (g/cm3) 0.0217 Compressive strength (kg/cm2) Foaming direction (■) 1.84 Vertical direction (⊥) 0.69 Dimensional stability (%
) -20℃×48 hours/direction -0.5⊥ direction
-2.1 70℃×48 hours ■Direction -0.6⊥ direction
+3.4 Taber set friability 227 Closed cell rate (% according to ASTM D-2856) 89 Foam fusion
Good cell characteristics
Good Comparative Example-1 Foaming was performed using polyol A-1 in the same manner as in Example-1.

The foam physical properties are as follows.

Density (g/cm2) 0.0227
Compressive strength (kg/cm2) ■Direction 1.34⊥
Direction 0.58 Dimensional stability (%) -20℃×48 hours■ direction -1.2⊥ direction
-25.7 70℃×48 hours ■Direction 4.6⊥Direction
9,2 Taber set fragility 76 closed cell ratio
80 tactile sensation
Bad cell characteristics
Bad Examples 2 to 3 In order to show the limit amount of polyol-B of the present invention, polyol A-2 and polyol B-5 were used in 95/5, 30/7.
Foaming was performed in the same manner as in Example 1 using polyols mixed at a ratio of 0.

The results are shown in Table-3. Comparative Examples 2 to 3 Foaming was performed using polyol A-2 and polyol B-5 alone in the same manner as in Example 1.

The results are shown in Table-3. As can be seen from Table 3, when polyol-A-2 was used alone, the foam feel, closed cell ratio, and brittleness were significantly reduced due to the coarseness and non-uniformity of the foam cells, and when polyol-B-5 was used alone, The mechanical properties and dimensional stability are poor.

When polyol B-5 is added to polyol A-2 in an amount of 5% or more of the total polyol, the brittleness, cell properties, feel, and closed cell ratio are improved, and when it exceeds 70%, mechanical properties and dimensional stability are decreased. come.

Example-4 80 parts of polyol A-2, 620 parts of polyol B-2,
1.0 parts of water, 40 parts of freon, silicone L-5420
1.5 parts, Dovecor 33LV 0.8 parts, DMEA
Hanel foaming was performed using 0.8 parts of TDI-TRC and 104.4 parts of TDI-TRC.

The panel was made by inserting a wooden frame with a thickness of 30 mm between two aluminum plates with a thickness of 5 mm and a length of 500 mm and a width of 500 mm.

After stirring the foaming ingredients thoroughly, it was poured into an aluminum panel kept at 30℃, and after foaming was completed, it was placed in an oven at 50℃ for 1 hour.
Let it harden for 0 minutes, then leave it at 25℃ for 2 hours,
It was immediately placed in a constant temperature bath to test its dimensional stability.

The foam physical properties are as follows.

Density Part of core 0.0286 Part of core with skin 0.0298 Dimensional stability (%) -20°C x 48 hours ■ direction +0.4 ⊥ direction -0.9 Thickness -4.7 70°C x 48 hours ■ Direction -0.2 ⊥ Direction +0.6 Thickness +2.2 Touch Good Good Cell Properties Good Examples -5 to 6 In order to show the limit amount of polyol B of the present invention, polyol A-2 and polyol B-2 were Panel foaming was performed in the same manner as in Example 4.

The results are shown in Table 4.

Comparative Examples 4 to 5 In the same manner as in Example 4, panel foaming was performed using polyol A-2 and polyol B-2, respectively.

The results are shown in Table 4. As can be seen from Table 4, when polyol A-2 is used alone, the density ratio is large, indicating a wide density distribution, and the dimensional stability is reduced in areas where the density inside the foam is low.

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

Polyol B-2 alone has good density ratio, cell properties, closed cell ratio, thermal conductivity, etc., but poor dimensional stability.

Examples 7 to 10 in which polyol A-2 and polyol B-2 are mixed and compared In the same manner as in Example 4, panel foaming was performed using the polyols listed in the table.

The results are shown in Table-5.

Comparative Example-6 Panel foaming was performed using polyol A-1 in the same manner as in Example-4.

The results are shown in Table-5.

When only polyol A-1 is used, it is difficult to balance gelation and foaming, and when the density is lowered, the cell state of the foam is poor and the texture is poor.

On the other hand, by using the polyol of the present invention, moldability,
A foam with good balance in processability, foam appearance, and physical properties was obtained.

Claims (1)

[Claims] 1. When producing low density rigid urethane foam from polyether polyol, polyisocyanate, and foaming aid, (A) sucrose and an active hydrogen compound having 2 to 4 active hydrogen atoms are used as polyether polyol. , obtained by reacting with propylene oxide, hydroxyl value 4
00 to 600 mgKOH/g polyether polyol and (B) an active hydrogen compound having 2 to 4 active hydrogen atoms obtained using an initiator, having a primary hydroxyl group at the terminal, hydroxyl value 400 to 800 mgKOH/ A method characterized by using a polyether polyol obtained by mixing the polyether polyol of (g) with a polyether containing a polyisocyanate and partially containing a urethane bond.