JP2005206691A - Method for producing rigid polyurethane foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rigid polyurethane foam having high dimensional stability, compressive strength and thermal insulation owing to using a specific polyol component even if water is used as a foaming agent. <P>SOLUTION: A method for producing the rigid polyurethane foam is provided, comprising carrying out a reaction between a polyol and an organic polyisocyanate in the presence of a foaming agent, a foam stabilizer and a catalyst. In this method, water is used as the foaming agent at 1-10 wt.% based on the total polyol, and the polyol component to be used is such that the total polyol includes 1-30 wt.% of a polyester polyol made up from diglycerol and a ≥2C polycarboxylic acid and the hydroxyl number of the total polyol is 200-800. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a rigid foamed polyurethane foam in which dimensional stability, compressive strength, and heat insulation are improved by adding a specific polyol component when water is used as a foaming agent.

  Conventionally, specific chlorofluorocarbons (CFCs) represented by trichloromonofluoromethane (CFC-11) and alternative chlorofluorocarbons (HCFC: hydrochlorofluorocarbon) have been often used as foaming agents for rigid foamed polyurethane foams. A rigid foamed polyurethane foam using a material has been widely used as a heat insulating material for refrigerators, freezers, buildings and the like because of its excellent low temperature dimensional stability and heat insulation. However, certain chlorofluorocarbons (CFC-11, etc.) have already been abolished for the reason that they cause the destruction of the earth's ozone layer, and alternative chlorofluorocarbons have been gradually reduced by regulations. Has been made.

  This is because HCFCs used as alternative blowing agents for CFCs are not zero in ozone depletion potential (ODP), and HFCs (hydrofluorocarbons), which are considered as one of the next generation blowing agents, are ODPs. Is zero, but has many problems such as relatively high global warming potential (GWP), many low boiling points for use as foaming agents, many of which are still unclear about toxicity Have.

  A technique using a hydrocarbon compound such as cyclopentane or n-pentane as a blowing agent in place of the above-mentioned halogenated hydrocarbons has also been proposed. There is a problem that the equipment cost becomes very expensive because a strict explosion-proof measure is required at the time of foam production.

On the other hand, water has been conventionally known as a foaming agent for rigid foamed polyurethane foams, and is partly used. However, in a system using water as a foaming agent, the use of an ether-based polyol compound obtained by ring-opening addition of propylene oxide or ethylene oxide, which has been conventionally used, deteriorates the dimensional stability of the rigid foamed polyurethane foam. was there. In order to improve the dimensional stability, a patent (for example, see Patent Document 1) using a low molecular weight aromatic polyester polyol as a polyol component is disclosed, but 1,1-dichloro-1- A blowing agent mainly composed of fluoroethane and / or 2,2-dichloro-1,1,1-trifluoroethane is used. In addition, an aliphatic polyester polyol having an average functional group number of 2.1 or more comprising an aliphatic polyhydric alcohol containing a polyhydric alcohol having 3 or more functional groups and a linear aliphatic polyvalent carboxylic acid having 2 or more carbon atoms is included as a polyol. Although a patent (for example, refer to Patent Document 2) is disclosed, CFC-11 alternative chlorofluorocarbon is used as a blowing agent, and water is not used alone as a blowing agent.
JP 7-25970 A JP-A-8-176265

  An object of the present invention is to provide a rigid foamed polyurethane foam having excellent dimensional stability, compressive strength, and heat insulation by blending a specific polyol component when water is used alone as a foaming agent. .

  As a result of intensive studies to solve the above problems, the present inventors have produced a rigid foamed polyurethane foam obtained by reacting a polyol with an organic polyisocyanate in the presence of a foaming agent, a foam stabilizer, and a catalyst. In the method, water is used as a blowing agent in an amount of 1 to 10% by weight based on the total polyol, and a polyester polyol composed of diglycerin and a polyvalent carboxylic acid having 2 or more carbon atoms is used as the polyol component. The present invention has been completed by finding that the above-mentioned problems can be achieved by using a polyol having a hydroxyl value of 200 to 800, which is contained in an amount of -30% by weight.

  The present invention can obtain a rigid foamed polyurethane foam excellent in strength, dimensional stability and heat insulation even when water is used as a foaming agent by blending a specific polyester polyol with a conventionally used polyol. It has the effect of being able to.

  Hereinafter, the text will be described in detail.

  The polyol used in the present invention contains 1 to 30% by weight of a polyester polyol composed of diglycerin and a polyvalent carboxylic acid having 2 or more carbon atoms, and the hydroxyl value of all polyols is 200 to 800. It is necessary. Examples of the polyvalent carboxylic acid having 2 or more carbon atoms include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, phthalic acid and isophthalic acid which are aromatic polyvalent carboxylic acids. Terephthalic acid and anhydrides thereof, and the above polyvalent carboxylic acids may be used alone or in combination. The synthesis of these polyester polyols is carried out according to a usual known method. The polyol to be reacted with the polyvalent carboxylic acid having 2 or more carbon atoms is diglycerin. When ethylene glycol, propylene glycol, glycerin or the like is used as the polyol, the number of functional groups of the polyester polyol is small, so that the crosslinking density of the foam is low. Dimensional stability and compressive strength are not improved. In addition, when the number of functional groups is greater than diglycerin, for example, tetraglycerin (functional group number 6), hexaglycerin (functional group number 8), decaglycerin (functional group number 12) or sorbitol (functional group number 6), the viscosity of the polyester polyol is higher. It becomes higher and difficult to be mixed with the isocyanate uniformly, and the reactivity with the isocyanate is accelerated, so that the filling property of the foam is impaired, and the foam has a non-uniform shape, and the dimensional stability, the compressive strength, and the heat insulating property are lowered. In addition, cell roughness may occur on the foam surface and the appearance may be impaired, and cracks and cavities may be generated inside the foam. When the polyester polyol composed of diglycerin and polyvalent carboxylic acid having 2 or more carbon atoms is less than 1% by weight with respect to the total polyol, the foam cross-link density is lowered, so the dimensional stability and compressive strength of the foam are improved. Not. In addition, when the polyester polyol composed of diglycerin and a polyvalent carboxylic acid having 2 or more carbon atoms exceeds 30% by weight with respect to the total polyol, the viscosity becomes high and it is difficult to uniformly mix, so that a good foam cannot be obtained. . In addition, when the hydroxyl value is less than 200, the crosslink density is decreased, so that the physical and mechanical strengths such as foam dimensional stability and compressive strength are decreased. In addition, the cell size is increased, so that the thermal conductivity is increased. The performance as a heat insulating material is deteriorated, and when the hydroxyl value of all polyols exceeds 800, the foam becomes brittle and a high strength foam cannot be obtained.

  Moreover, as another polyol used for the polyol of this invention, there is no limitation in particular and a well-known thing can be used. For example, polyols such as glycerin, diglycerin, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, trimethylolpropane, sucrose, sorbitol, pentaerythritol, and / or the above polyols such as ethylene oxide, propylene oxide, butylene oxide, etc. Examples include polyether polyols obtained by addition polymerization of alkylene oxide. In addition, an alkylene oxide such as ethylene oxide, propylene oxide, and butylene oxide is added to polyvalent amines such as ammonia, ethylenediamine, diethylenetriamine, triethylenediamine, trimethyldiethylenetriamine, polyetherpolyamine, toluenediamine, diphenylmethanediamine, and xylenediamine. Examples include polyether polyols obtained.

  In the present invention, it is necessary to use 1 to 10% by weight of water as a blowing agent based on the total polyol. When the amount of water with respect to the total polyol is less than 1% by weight, the swelling of the foam is suppressed, and when it exceeds 10% by weight, the reaction is accelerated, and the foam is cracked and a uniform foam cannot be obtained. That is, in a method for producing a rigid foamed polyurethane foam obtained by reacting a polyol and an organic polyisocyanate in the presence of a foaming agent, a foam stabilizer, and a catalyst, the polyol component contains diglycerin and 2 carbon atoms relative to the total polyol. It comprises 1 to 30% by weight of a polyester polyol composed of the above polyvalent carboxylic acid, and is composed of a polyol having a hydroxyl value of 200 to 800 of all the polyols. By using the weight%, it is possible to obtain a rigid foamed urethane foam having good dimensional stability, compressive strength, and heat insulating properties as the object of the present invention. Among them, the polyester polyol synthesized from diglycerin and succinic acid and / or the polyester polyol synthesized from diglycerin and phthalic acid is included in the total polyol in an amount of 2 to 10 parts by weight, and the hydroxyl value of the total polyol is 400 to 600. It is particularly preferable to use 2 to 6% by weight of water as a blowing agent with respect to the total polyol.

  Any known organic polyisocyanate can be used, but the most common ones are toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). TDI can also be a mixture of isomers or crude TDI containing a multifunctional tar. Moreover, as MDI, polymeric MDI containing a polynuclear body of 3 or more nuclei can be used in addition to a pure product mainly composed of 4,4'-diphenylmethane dicycyanate. NCO / OH = 0.70 to 2.00 (equivalent ratio) of the organic polyisocyanate and active hydrogen in the raw material is particularly suitable.

  Examples of the catalyst include trimethylaminoethylpiherazine, triethylamine, tripropylamine, N-methylmorpholine, N-ethylmorpholine, triethylenediamine, N, N, N ′, N′-tetramethylethylenediamine, N, N An amine-based urethanization catalyst such as N, N ′, N′-tetramethylhexamethylenediamine can be preferably used. Also, metal compound catalysts such as organotin compounds and urethanization catalysts such as organic acids can be used. These catalysts can be used alone or in combination, and the amount used is preferably from 0.0001 to 10.0 parts per 100 parts of the compound having active hydrogen.

  Examples of the foam stabilizer include silicone foam stabilizers and fluorine-containing compound foam stabilizers, and the amount used is 0.1 to 10 parts with respect to 100 parts of the total of all active hydrogen compounds and organic polyisocyanate. . In addition, flame retardants, plasticizers, stabilizers, colorants, and the like can be added as necessary.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples.

<Examples 1-4, Comparative Examples 1-6>
<Synthesis example>
Polyester polyol A was synthesized by the following method.
332 g (2 mol) of diglycerin, 118 g (1 mol) of succinic acid, and 0.045 g of sodium hydroxide were charged into a four-necked 500 ml flask equipped with a nitrogen inlet tube, a thermometer, and a stirrer. min), the reaction was carried out at 200 ° C. while water produced as a by-product was distilled out of the system to obtain the following polyester polyol A. The reaction was terminated when the acid value of the reaction product was 1.0 or less.
Polyester polyol A: Transparent viscous liquid, hydroxyl value 780, viscosity 50000 mPa · s (25 ° C.), hue APHA20
In addition, polyester polyols B and C used in Examples and polyester polyols D and E used in Comparative Examples were also synthesized in accordance with the above synthesis method, and the following were obtained. In addition, the commercially available polyether polyol was used for polyol FJ used for the Example and the comparative example.
Polyester polyol B: Polyester polyol synthesized from diglycerin and succinic acid, transparent viscous liquid, hydroxyl value 1140, viscosity 30000 mPa · s (25 ° C.), hue APHA20
Polyester polyol C: Polyester polyol synthesized from diglycerin and phthalic acid, transparent viscous liquid, hydroxyl value 710, viscosity 60000 mPa · s (25 ° C.), hue APHA20
Polyester polyol D: Polyester polyol synthesized from ethylene glycol and succinic acid, transparent viscous liquid, hydroxyl value 770, viscosity 30000 mPa · s (25 ° C.), hue APHA20
Polyester polyol E: polyester polyol synthesized from decaglycerin and phthalic acid, transparent viscous liquid, hydroxyl value 760, viscosity 120,000 mPa · s (25 ° C.), hue APHA20
Polyether polyol F: polyether polyol obtained by adding propylene oxide to toluenediamine, transparent viscous liquid, hydroxyl value 487, viscosity 3500 mPa · s (25 ° C.)
Polyether polyol G: Polyether polyol obtained by adding propylene oxide to ethylenediamine, transparent viscous liquid, hydroxyl value 438, viscosity 6870 mPa · s (25 ° C.)
Polyether polyol H: polyether polyol obtained by adding propylene oxide to glycerin, transparent viscous liquid, hydroxyl value 405, viscosity 360 mPa · s (25 ° C.)
Polyether polyol I: Polyether polyol obtained by adding propylene oxide or ethylene oxide to sorbitol, transparent viscous liquid, hydroxyl value 480, viscosity 700 mPa · s (25 ° C.) polyether polyol J: polyether obtained by adding propylene oxide to glycerin Polyol, transparent viscous liquid, hydroxyl value 56, viscosity 497 mPa · s (25 ° C)

  After blending a predetermined amount of polyol, water as a foaming agent, silicone foam stabilizer, and catalyst as N, N, N ′, N′-tetramethylethylenediamine as shown in Table 1, 1.05 based on the total active hydrogen. An amount of polymethylene polyphenyl isocyanate containing double equivalent isocyanate groups was mixed at high speed for 10 seconds at a liquid temperature of 20 ° C., placed in a wooden box of 250 mm × 250 mm × 200 mm, foamed and evaluated. The evaluation results are shown in Table 1.

  The measurement conditions for the various characteristic values of the rigid foamed polyurethane foam are as follows.

  Dimensional stability: The rate of dimensional change of the foam after standing for 72 hours at 70 ° C. and 95% RH on a test piece of rigid foam polyurethane foam cut to 100 mm × 100 mm × 40 mm was measured.

  Compressive strength: measured in accordance with JIS K 7220. The compression strength of the rigid foamed polyurethane foam test piece cut to 60 mm × 60 mm × 35 mm was measured using a universal testing machine.

  Closed cell ratio: A test piece of rigid foamed polyurethane foam cut to 20 mm × 20 mm × 25 mm was measured using an air-comparing hydrometer.

  Thermal conductivity: A test piece of rigid foamed polyurethane foam cut to 200 mm × 200 mm × 30 mm was measured with a thermal conductivity measuring device.

Foam state: The appearance of the foam (cell roughness) and the inside of the foam (cracks and cavities) were observed.
○: There was no cell roughness and the inside of the foam was uniform.
X: Cell roughening was severe, and cracks and cavities were generated inside.

By blending the polyester polyol of the present invention, even when water is used as a foaming agent, a rigid foamed polyurethane foam excellent in strength, dimensional stability and heat insulation can be obtained. It can be suitably used as a heat insulating material.

Claims (1)

In a method for producing a rigid foamed polyurethane foam obtained by reacting a polyol with an organic polyisocyanate in the presence of a foaming agent, a foam stabilizer, and a catalyst, water is used as a foaming agent in an amount of 1 to 10% by weight based on the total polyol. And 1 to 30% by weight of a polyester polyol composed of diglycerin and a polycarboxylic acid having 2 or more carbon atoms as a polyol component, and the hydroxyl value of all polyols is 200 to 800. A method for producing a rigid foamed polyurethane foam.