JPS5915425A - Elastic support for low-temperature structure - Google Patents

Abstract

PURPOSE:An elastic support for low-temperature structures excellent in elastic properties at low temperatures, comprising a low-expansion ratio elastomer obtained by reacting an organic polyisocyanate with a polyether-polyol and a chain extender at a specified ratio in the presence of water. CONSTITUTION:An elastic support comprisng a low-expansion ratio polyurethane elastomer, bulk density of 0.6-0.95g/cm<3>, obtained by reacting (a) an organic polyisocyanate with (b) a polyether-polyol (average functionality of 2.5-3.5 and number-average MW of 4,500-8,500) and (c) a chain extender at a ratio to provide an NCO index of 90-110 in the presence of water as a blowing agent. The above elastomer is extremely excellent in low-temperature properties; is not brittle down to about -80 deg.C; and has a spring constant which is low in temperature dependency and remains nearly constant over a wide range of temperature (for example, -40-+40 deg.C). Besides, this elastomer is excellent resistances to abrasion, hydrolysis, ozone, flexing fatigue, etc.

Description

[Detailed description of the invention] The present invention relates to a novel elastic support for low temperature structures.

More specifically, it is comprised of a low foaming polyurethane distomer of the following types. It is particularly suitable as a side wall buffer pad or bottom support for liquefied propane gas (LPG) tanks and liquefied natural gas (LNG) tanks.

This invention relates to an elastic support for low-temperature structures that has excellent elastic properties at low temperatures.

Conventional elastic bearings for civil engineering structures, such as road bridge bearings, side wall cushioning/rad and bottom bearings of LPG tanks and LNG tanks, are usually made of neograin rubber or ERR.
Synthetic rubbers such as Particularly in the case of ultra-low temperature structures such as %LPGLPG Tank G Tank, the supporting body is exposed to low temperatures of about -40°C or lower even outside the insulation material.

Low-temperature properties (especially the constant,
(compression set, hardness) are required. In general, elastic bodies exhibit good elasticity due to active molecular motion above room temperature, but as the temperature decreases, molecular motion becomes inactive, and below a certain temperature, the motion stops, resulting in what is called freezing (secondary transition). It is well known that this occurs (this temperature is the second-order transition temperature Tt).

However, as a guide to cold resistance, the embrittlement temperature Tb, which is the temperature at which the material becomes brittle, is slightly higher than the secondary transition temperature.
However, this embrittlement temperature differs depending on the type of elastic body, and the embrittlement temperature (Tb) of synthetic rubber conventionally used as an elastic support is approximately as follows.

rb(''c) Neoglen GM -40 Neoglene ILS -19 SBE -65 to -58 Polyurethane Approximately -80 As mentioned above, the embrittlement temperature of synthetic comb is
Because it is higher than or almost the same as the surface temperature of the PG tank,
It is not fully satisfactory as a support for a low-temperature structure such as an LNG tank or an LPG tank. NBR, a type of synthetic rubber, is
At around 0°C, the compression set already reaches 40%, making it almost impossible to use as an elastic body.

Therefore, the present inventors conducted intensive studies to develop an elastic material, gold, with excellent low-temperature properties.As a result, the following components: (α) organic polyisocyanate, (b) an average number of functional groups of 2.5 to 3.5 were found. and a polyether polyol having a number average molecular weight of 4.500 to 8.500.

and (σ) chain extender 2, 1 in a ratio such that the NGO index is 90 to 110.
The low-foaming polyurethane elastomer with a bulk density of 0.6 to 0.95 F/i obtained by reacting in the presence of water as a foaming agent has extremely excellent low-temperature properties and does not become brittle up to around -80°C. , the spring constant has little temperature dependence and remains almost constant over a wide temperature range (e.g. -40°C to +40°C), and has good abrasion resistance, hydrolysis resistance, ozone acclimatization,
It has been found that it has excellent physical properties such as LTI bending resistance, and is extremely suitable as an elastic support for low-temperature structures such as side wall buffer notches and bottom supports of LPG tanks and LNG tanks.1 The present invention I was able to complete it.

Hereinafter, the structure of the low foaming polyurethane elastomer suitable for the purpose of the present invention will be explained in detail.

The polyurethane elastomer used in the present invention has an average functionality of 25 to 3.5 and a number average molecular weight of 4500 to 85.
00 polyhydric alcohol, organic polyisocyanate, urethanization catalyst, chain extender.

Formed from a composition comprising a blowing agent and a foam stabilizer.

If the functionality number of the polyhydric alcohol is less than 25, the resulting urethane elastomer will have a large compression set, which is an important property as an elastic support for low-temperature structures, and is therefore not suitable. Shoe soles, etc. (The polyurethane elastomer used is often a polyhydric alcohol with a functional group number close to 2; The number of groups must be at least 25. On the other hand, if the number of functional groups of the polyhydric alcohol used exceeds &5, the resulting nidistomer tends to become extremely hard and there is a greater risk of it breaking due to compression. Therefore, the preferred number of functional groups is 2.
．． It ranges from 8 to 3.3. In addition, polyhydric alcohols with a number average molecular weight of 4,500 to 8,000 are used, but if the number average molecular weight is less than 4,500, only polyurethane elastomers () and mer, which have low vibrational energy absorption properties especially at low temperatures, can be obtained. I can't do it. This is thought to be because the density of chemical crosslinking points is high and the behavior approaches that of a perfectly elastic body. On the other hand, if the number average molecular weight exceeds 8,500'i, the resulting polyurethane elastomer will have lower elastic properties, will be more likely to undergo plastic deformation, and will have an increased compression set, particularly at low temperatures, which is not preferred. The preferred number average molecular weight range of the polyhydric alcohol is 4,500 to 61,500.

As the polyhydric alcohol that can be used in the present invention, those known per se can be used.

For example, low molecular weight active hydrogen compounds containing at least two active hydrogen atoms such as lower aliphatic polyhydric alcohols having 2 to 6 carbon atoms such as glycerin and trimethylolgulonone or ethylenediamine, ethylene oxide, oxidized globulin, etc. It is obtained by addition polymerization of an oxyalkylene compound having 2 to 4 carbon atoms such as gyrene. So-called polyether polyols can be used. This polyether polyol can also be used in combination with a polyester polyol or a hydroxy-terminated liquid polygetadiene, if necessary.

In addition, in the present invention, low foaming y with excellent low temperature properties
+? To obtain urethane elastomer.

It is essential to use chain extenders. Chain extender (
l'j: Reacts with isocyanate to form a hard segment mainly composed of hydrogen bonds through urethane bonds or base bonds, and becomes an important factor in controlling elastic properties at low temperatures. According to the research conducted by the present inventors, in the case of the combination with the above-mentioned polyether polyol, the blending amount of the chain lengthening agent is determined according to the unit type of the resulting polyurethane elastomer.
:J expressed as the commercial concentration of active hydrogen in the chain extender, 0.8X 10-'' to 2. IX 10-' equivalents/y, preferably Ul, IX 10-'' to 1.
7
．． If it is lower than 8X10-" equivalent/f, the chain length extension effect will not be sufficient, so the strength of the resulting low foaming polyurethane elastomer will be extremely low and it will be difficult to put it into practical use.
When the concentration is higher than 0-'I/2, the number of hydrogen bonds increases, so the strength of the resulting polyurethane elastomer is improved, but it becomes an extremely hard elastomer, and the fatal defect 4 is compression permanentness at low temperatures. Strain and cyclic compression fatigue properties deteriorate.

As such chain extenders, relatively low molecular weight substantially 2
~tetrafunctional, especially difunctional compounds, i.e. diols.

Diamines etc. are used, for example.

Ethylene glycol, gulo gyrengelicol, gurono 9
Examples include fluorine-containing alcohol, butanediol, hydroquinone, hydroxyethylquinone ether, methylenebis-(0-dichloroaniline), quadrol, ethylenecyamine, triethanolamine, among others, L-white having 2 to 6 carbon atoms. Chain alkyleneduols, especially
Ethylene glycol or 1,4-butanediol are preferred.

On the other hand, as the organic polyisocyanate, those commonly used for urethane elastomers can be used. For example, 4
．． 4'-diphenylmethane diisocyanate (MDI)
, naphthylene diisocyanate <NDI), lylene diisocyanate (TDI)% hexamethylene diisocyanate, etc., and a mixture of two or more of these may also be used. Among them, aromatic diincyanates such as MDI, MDI and TDI, especially MDI
is suitable. It is more advantageous to use MDI in its pure state than in its crude state.

The polyisocyanates can also be used as precursors, precondensed with polyether polyols, ie prepolymers or semi-prepolymers. In any case, the amount of organic polyisocyanate used is 90 to 110, preferably 95 to 105, expressed in NCO index.
Advantageously, it is within the range of .

The low foaming polyurethane elastomer of the present invention can use water as a foaming agent.

The bulk density targeted by the present invention is 0.6 to 0.9 ti f
/ / The amount of blowing agent required to produce a ctI polyurethane elastomer can be easily determined by a commercial person, but is generally between 3.3 x 10-' per unit weight (f) of the resulting polyurethane elastomer. 3.0×10
It can be used within the range of 8f.

The urethanization catalyst used is one used in ordinary urethanization reactions, that is, tertiary amine compounds, organometallic compounds, etc. For example, triethylenediamine. Diazarbicycloundecene, N-methylmorpholine, N, N-f
) Methylethanolamine, tin octylate, diptyltin laurate, and the like. The amount of catalyst used can vary widely depending on the desired reaction rate, amount of foaming the urethane elastomer, atmospheric conditions (temperature, etc.).

It is necessary to adjust the amount used depending on the humidity, etc., and it is easy to select all of them.

The low foaming polyurethane elastomer of the present invention may contain a cell stabilizer such as a silicone surfactant as appropriate, and may also contain a pigment such as carbon black.

Each of the above-mentioned components can be reacted by a method known per se. For example, after intimately mixing liquids A and B having the compositions shown below, the mixture is poured into a suitable mold and allowed to foam and harden. This foam curing can normally be carried out at room temperature, but if necessary, it may be carried out while being heated to a temperature of up to about 70°C. Foam curing is generally completed within 1 to 2 hours.

Once the foaming and curing is completed, the mold is removed.

A component composition polyether polyol too, o Weight part average molecular weight = a, 5oo) Ethylene glycol 4-20 (chain extender) Water (foaming agent) 0.1-0.5 Foam stabilizer (vAJ is silicone surfactant) 0.1 to 1 Triethylene cyakin (urethanization catalyst) 0.1 to 0.5 Part B composition polyisocyanate/poly NGO index ether polyol pre-90 to 110 polymer (e.g. 4. By combining 4'-diphenylmethane diisocyanate and the above-mentioned polyether polyol, an elastic support made of a low-foaming polyurethane elastomer can be obtained.Most of the air bubbles in the low-foaming polyurethane elastomer molded in this way are Desirable physical properties (at room temperature) of the closed-cell elastomer include the following.

■ High density Ill: 0. 6-0. 9 5
f / cr ■ Tensile strength: at least 5 kg
/cri or more, preferably 10 to 60 kg/crl ■ Spring constant: unit area 5 kg/cri or more.

Preferably 10-5oky/bow/shoulder ■ Compression set: 25% or less, preferably 15% or less ■ Fatigue strength: 1 (Inn or less, preferably 1.0 m
As mentioned above, the low foaming polyurethane elastomer of the present invention has excellent low-temperature properties, and representative properties include the following.

As described above, the low-foam polyurethane elastomer V according to the present invention has excellent low-temperature properties (7), and can be extremely advantageously used as an elastic support for low-temperature structures such as LPG tanks and LNG tanks. However, taking as an example the case where the elastic support of the present invention is used as an elastic support in an underground LNG tank, the method of use thereof will be explained as follows.

, 50,000) underground LNG tanks are constructed with insulation materials such as polyurethane foam, as seen in Figure 1.
The tank body 1, which consists of a menglen l covered with
A reinforced concrete IJ with a thickness of approximately 4 to 7 to 7 L was constructed at a depth of 59 m.The structure is such that a reinforced concrete floor plate 1 is installed on top of the tank, and the side surface above the tank body is surrounded by a reinforced concrete side wall 7. .

The LNG stored in the Kunku l is a liquid with an ultra-low temperature of approximately -162℃, and although the outer periphery and bottom of the tank's men's tank are covered with a fairly thick insulation material, the insulation is 100%. Temperatures near the surface of the reinforced concrete floorboard 60 can reach approximately -40°C.

However, depending on the amount of LNG in the tank, the reinforced concrete floorboards experience temperature changes from room temperature to approximately -40°C.
This will result in expansion and contraction of up to about 20 meters.

Therefore, a clearance 8 is provided between the reinforced concrete IJ-to floor plate 6 and the reinforced concrete side wall 7.

It is necessary to prevent the stiffness of the reinforced concrete floor plate 6 from touching the reinforced concrete side wall 7. In order to maintain a uniform clearance 8 of C, supports A and B are inserted at the joint between the reinforced concrete floor plate 6 and the reinforced concrete side wall 7, as shown in Figure #fJ1.

As mentioned above, this support A and B (approximately -40℃
Since it is exposed to low temperatures, it must maintain sufficient elasticity and withstand displacement even at such low temperatures. In this point 1, the support provided by the present invention-1 has unique low-temperature characteristics, and is suitable for use in LNG tanks and LP tanks as described above.
It is suitable as a support for low-temperature structures such as G tanks.

Next, the present invention will be further explained with reference to examples.

Example: A polyurethane elastomer stock solution having the following stock solution composition was poured into a mold of a predetermined size, and the mold was made into a mold of 25 x 600 x 800.
A foam of yum size was molded.

The density of the resulting foam was 0.85 f/crA.

Composition of polyurethane elastomer stock solution (Liquid A) Polyether polyol i o o o.

Ethylene glycol 12.0 water
025
(Liquid B) (Note 1) Glycerin/propylene oquinide/ethylene oxide addition polymer with a number average molecular weight of 5500 (total 2) Silicone surfactant (Note 3) 4,4'-diphenylmethane soisocyanate and the above Note 1 Isocyanate-terminated precondensate with the polyether polyol described in , residual isocyanate - 816% by weight Ta.

The hardness (SRIS-0101) and compression set (JIS A
-6301) and spring constant (JISK-6385) are shown in the table below in comparison with Neograin plate rubber (JIS standard product), which has been conventionally used as a support for LPG tanks and LNG tanks.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of an underground LNG tank. Patent applicant: Nisshinbo Co., Ltd. Rod 1 diagram

Claims (1)

[Claims] 1. (α) Organic polyisocyanate. (b) The average number of functional groups is 2. ．． A polyether polyol having a number average molecular weight of 5 to 365 and a number average molecular weight of 4,500 to 8,500. and (6) chain extender q, 1 at a ratio such that the NGO index is 90 to 110.
An elastic support for a low-temperature structure made of a low-foaming polyurethane elastomer having a bulk density of 0.6 to 0.95 t/r:tA obtained by reaction in the presence of water as a foaming agent. 2. The elastic support for a low temperature structure according to claim 1, wherein the organic polyisocyanate is 4,4'-diphenylmethane diisocyanate. & The elastic support for a low-temperature structure according to claim 1, wherein the polyether polyol has an average number of functional groups of 28 to 3.3 and a number average molecular weight of 4,500 to 6,500. 4. The elastic support for a low-temperature structure according to claim 1, wherein the chain extender is a low molecular weight bifunctional compound. 5. The low foaming polyurethane elastomer is 5-50T
The elastic support for a low-temperature structure according to claim 1, having a spring constant per unit area of ql/cIIL-crli.