JP2008260842A - Polyisocyanate composition for rigid polyurethane foam made by foaming using cyclopentane, and method for producing rigid polyurethane foam by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a rigid polyurethane foam, suitable for a foaming system using cyclopentane and water, which is friendly to the global environment, using a polyisocyanate composition having excellent storage stability, and providing the rigid polyurethane foam having good thermal conductivity characteristics. <P>SOLUTION: The polyisocyanate composition for the cyclopentane-foamed rigid polyurethane foam contains an isocyanate group-containing prepolymer formed by reacting a polymeric MDI (A1) with a low-molecular weight polyol (A2) containing a methyl group and having ≤200 molecular weight, and has 800-2,500 mPa s viscosity at 25°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polyisocyanate composition for rigid polyurethane foam for foaming cyclopentane. More specifically, for rigid polyurethane foams for foaming cyclopentane, which is compatible with the foaming system using cyclopentane and water that are friendly to the global environment, can obtain rigid polyurethane foams with excellent storage stability and good thermal conductivity. The present invention relates to a polyisocyanate composition.

Rigid polyurethane foam is useful as a heat insulating material, and has excellent moldability and processability. From heat insulation of electric refrigerators to insulation of buildings, low-temperature warehouses, storage tanks, freezing ship piping, etc. Used in a wide range of fields. Its thermal conductivity has been improved year by year, and at present, it has reached 0.0215 W / mK (see Non-Patent Document 1) at the product level, and it is said that it has the highest thermal insulation performance as a heat insulating material used near room temperature. It has been broken. However, against the background of the recent increase in energy saving, there is an increasing demand for further lowering the thermal conductivity of the heat insulating material.
Uwa Thermal Engineering Co., Ltd. website, product information, cyclopentane February 1, 2006 Search URL: http://www.uwa-ud.co.jp/cyclopentane.htm

  Conventionally, in order to produce such a rigid polyurethane foam, a foaming process is performed by mixing and reacting a component A mainly composed of a polyol, a catalyst, a foaming agent and a foam stabilizer and a component B mainly composed of an organic isocyanate. A one-shot method is generally used in which a foam is formed by proceeding in parallel with a curing process. In the production of such rigid polyurethane foam, trichloromonofluoromethane (hereinafter abbreviated as R-11) has been mainly used as a foaming agent in the past, but conventional fluorocarbons represented by R-11 have been used. Is known to be chemically stable, diffuses to the stratosphere and destroys the ozone layer, and has recently been banned as a major cause of the destruction of the global environment.

  In recent years, therefore, diligent research has been conducted on a foaming agent that replaces such a fluorocarbon. For example, 1,1-dichloro-1-fluoroethane (hereinafter referred to as HCFC) which is hydrochlorofluorocarbon (hereinafter abbreviated as HCFC). 141b) and methylene chloride are listed as candidates for R-11.

  However, since the HCFC mentioned above still contains chlorine atoms in the molecule, it has less influence on the ozone layer than R-11, but it still has the property of destroying the ozone layer, so it is also produced and used. Has been decided to cancel. Therefore, from the viewpoint of protecting the global environment, the use of a foaming agent that does not affect the destruction of the ozone layer has been newly proposed. In some applications, hydrocarbons that do not contain any chlorine atoms and do not risk the destruction of the ozone layer. For example, cyclopentane is introduced and applied.

  However, cyclopentane is optimal as a foaming agent friendly to the global environment, but has some problems. In particular, because of the high thermal conductivity of the gas of cyclopentane itself, the heat insulation performance of the rigid polyurethane foam simply using cyclopentane is inferior to that using the conventional HCFC-141b. ing.

  In order to improve the thermal conductivity of the cyclopentane foamed foam, it has been proposed to reduce the compatibility between the foam raw material and cyclopentane, thereby miniaturizing the cell. Patent Document 1 includes (1) an organic polyisocyanate composed of aromatic polyisocyanate, (2) a polyol composed of polyether polyol and / or polyester polyol, (3) foaming agent, (4) foam stabilizer, catalyst and others. In which a foaming agent (3) is cyclopentane and water, and a polyol (2) is a polyether polyol and / or polyester having low compatibility with cyclopentane A method for producing a rigid polyurethane foam, which is a polyol and is characterized by mixing and dispersing cyclopentane in a polyol premix comprising components (2) to (4), has been proposed.

JP 2000-128951 A

  An object of the present invention is to provide a polyisocyanate composition for rigid polyurethane foam for foaming cyclopentane, which is capable of obtaining a rigid polyurethane foam that is friendly to the global environment and has good heat conduction characteristics.

  That is, this invention is shown by the following (1)-(3).

(1) An isocyanate group-containing prepolymer produced by reacting a polymeric MDI (A1) with a low molecular polyol (A2) containing a methyl group and having a molecular weight of 200 or less, and having a viscosity at 25 ° C. of 800 to 2, A polyisocyanate composition for rigid polyurethane foam for foaming cyclopentane, characterized by being 500 mPa · s.

(2) Low molecular polyol (A2) is 1,2-propanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-propanediol The polyisocyanate composition for rigid polyurethane foam for foaming cyclopentane according to claim 1, wherein the polyisocyanate composition is selected from dipropylene glycol.

(3) In the method for producing a rigid polyurethane foam in which polyisocyanate and polyol are reacted / foamed in the presence of a catalyst and a foaming agent, the polyisocyanate is the polyisocyanate composition according to (1) or (2), and foaming is performed. A method for producing a rigid polyurethane foam, wherein the agent is used in combination with cyclopentane and water.

  According to the present invention, it has become possible to provide a rigid polyurethane foam having good heat conduction characteristics by using cyclopentane and water which are friendly to the global environment as a foaming agent.

  The polyisocyanate composition for rigid polyurethane foam for foaming cyclopentane of the present invention is an isocyanate group-containing prepolymer produced by reacting polymeric MDI (A1) with a low molecular polyol (A2) having a methyl group and having a molecular weight of 200 or less. It consists of a polymer (A) and a foam stabilizer (B), and the viscosity at 25 ° C. is 800 to 2,500 mPa · s.

  This polymeric MDI means a mixture of organic isocyanate compounds with different degrees of condensation obtained by converting an amino group to an isocyanate group by phosgenation or the like of a condensation mixture (polyamine) obtained by the condensation reaction of aniline and formalin. The composition of the finally obtained polymeric MDI can be changed by changing the raw material composition ratio and reaction conditions during the condensation. The polymeric MDI used in the present invention has different numbers of reaction liquids after conversion to isocyanate groups, or removal of the solvent from the reaction liquids, or bottoms obtained by distilling and separating part of the MDI, reaction conditions and separation conditions, etc. It may be a mixture of seeds. Further, a part of the isocyanate group may be modified to biuret, allophanate, carbodiimide, oxazolidone, amide, imide or the like.

  The average number of functional groups of polymeric MDI is 2.3 or more, and preferably the number of functional groups is 2.3 to 3.1. The isocyanate content is 28 to 33% by mass, preferably 28.5 to 32.5% by mass.

  Polymeric MDI contains diphenylmethane diisocyanate (MDI) having two benzene rings and two isocyanate groups in one molecule, a so-called dinuclear component. The isomers constituting MDI are 2,2'-diphenylmethane diisocyanate (hereinafter abbreviated as 2,2'-MDI), 2,4'-diphenylmethane diisocyanate (hereinafter abbreviated as 2,4'-MDI), There are three types of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as 4,4'-MDI). The isomer composition ratio of MDI is not particularly limited, but the 4,4′-MDI content is preferably 70% by mass or more, preferably 90 to 99.9% by mass because the strength of the resulting foam is improved. . The MDI content of polymeric MDI and the isomer composition ratio of MDI can be determined from a calibration curve based on the area percentage of each peak obtained by GPC or gas chromatography (hereinafter abbreviated as GC).

  The polymeric MDI used in the present invention has a peak area ratio of 20 to 70% of a dinuclear (having two benzene rings in one molecule) component in gel permeation chromatography (hereinafter abbreviated as GPC). And preferably 25-65%. When the peak area ratio of the binuclear body exceeds 70%, the strength of the rigid polyurethane foam obtained is lowered and the brittle body tends to become brittle. On the other hand, when it is less than 20%, the viscosity of the resulting polyisocyanate increases, and the filling property into the mold tends to decrease.

  In the present invention, if necessary, a polyisocyanate other than the above-mentioned polymeric MDI can be used. Examples include MDI isocyanurate-modified products, uretonimine-modified products, allophanate-modified products, and the like. In addition, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, tetramethylxylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, etc. Aromatic diisocyanates, tetramethylene diisocyanates, hexamethylene diisocyanates, 3-methyl-1,5-pentane diisocyanates, lysine diisocyanates and other aliphatic diisocyanates, isophorone diisocyanates, hydrogenated tolylene diisocyanates, hydrogenated xylene diisocyanates, hydrogenated diphenylmethane diisocyanates, etc. And alicyclic diisocyanates. In addition, these polymeric bodies, urethanized products, ureaated products, allophanated products, biuretized products, carbodiimidized products, uretoniminate products, uretdioneized products, isocyanurated products, and the like, and a mixture of two or more of these may be mentioned.

  The low molecular polyol (A2) used in the present invention is a low molecular polyol containing a methyl group and having a molecular weight of 200 or less. By subjecting polymeric MDI to urethane modification with a low molecular polyol, a highly polar urethane group is imparted to the isocyanate. For this reason, the compatibility of isocyanate and cyclopentane is lowered, and cyclopentane is finely dispersed in the system. Since the thermal conductivity of the resulting foam is better as the cells are finer, the rigid polyurethane foam using the polyisocyanate composition of the present invention has a good thermal conductivity. The methyl group prevents aggregation between molecules during the production of the isocyanate group-containing prepolymer, and contributes to the storage stability of the polyisocyanate composition.

  Examples of such a low molecular polyol (A2) include 1,2-propanediol, 1,3-butanediol, neopentyl glycol, 3-methyl-1,5-propanediol, dipropylene glycol, 2-methyl-1 , 3-propanediol, hydrogenated bisphenol A, 2,4-dimethyl-1,5-pentanediol and the like. In the present invention, 1,2-propanediol, 1,3-butanediol, 3-methyl-1,5-propanediol, dipropylene glycol, and 2-methyl-1,3-propanediol are preferable.

  The polyisocyanate (A) used in the present invention is obtained by synthesizing an isocyanate group-containing prepolymer by reacting the above-described polymeric MDI (A1) with a low molecular polyol (A2) at 40 to 100 ° C. . The ratio of the polymeric MDI (A1) and the low molecular polyol (A2) is preferably NCO / OH = 100/1 to 1000/1 in terms of the molar ratio of isocyanate group (NCO) to hydroxyl group (OH). When the amount of OH is too small, the amount of urethane groups introduced is insufficient, so that cyclopentane is not refined in the system and the heat conduction characteristics of the resulting foam are not improved. When there is too much OH, since the viscosity of the polyisocyanate obtained becomes high, liquid feeding in the actual production becomes difficult. The isocyanate content of the polyisocyanate (A) thus obtained is preferably 25 to 30% by mass, particularly preferably 26 to 29% by mass.

  Various additives and auxiliaries such as antioxidants, ultraviolet absorbers, flame retardants, plasticizers, pigments / dyes, antibacterial agents / antifungal agents, and the like may be added to the polyisocyanate composition of the present invention as necessary. You can also.

  The method for producing a rigid polyurethane foam of the present invention is a method for producing a rigid polyurethane foam in which a polyisocyanate and a polyol are reacted / foamed in the presence of a catalyst and a foaming agent, wherein the polyisocyanate is the aforementioned polyisocyanate composition, The blowing agent is characterized by using cyclopentane and water in combination.

  There is no restriction | limiting in particular as a polyol, The thing used for the well-known urethane industry can be used, For example, polyester polyol, polyether polyol, polycarbonate polyol etc. are mentioned. In consideration of foam strength and the like, a low molecular polyol, a low molecular polyamine, a low molecular amino alcohol, or the like can be used in combination.

  The blowing agent is cyclopentane and water. When the foaming agent is cyclopentane only, the resulting foam tends to shrink. The amount of the blowing agent used is 0.1 to 30% by mass of cyclopentane and 0.1 to 3% by mass of water based on the polyol.

  As the catalyst, a known catalyst usually used for urethane foaming can be used. For example, as a urethanization catalyst, N-methylimidazole, trimethylaminoethylpiperazine, tripropylamine, tetramethylhexamethylenediamine, triethylenediamine, triethylamine, N-methylmorpholine, dimethylcyclohexylamine, dibutyltin diacetate, dibutyltin dilaurate, etc. And metal complex compounds such as acetylacetone metal salts. Trimerization catalysts include 2,4,6-tris (dimethylaminomethyl) phenol, triazines such as 1,3,5-tris (dimethylaminopropyl) hexahydro-s-triazine, 2,4-bis (dimethylamino) Methyl) phenol, amine compounds such as potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, potassium acetate, sodium acetate, 2-ethylaziridine and the like, and quaternary compounds such as tertiary amine carboxylates Examples include ammonium compounds, lead compounds such as diazabicycloundecene, lead naphthenate and lead octylate, alcoholate compounds such as sodium methoxide, phenolate compounds such as potassium phenoxide, and the like. These catalysts can be used alone or in combination of two or more. The amount of the catalyst used is appropriately 0.01 to 15% by mass based on the polyol.

  Furthermore, for example, carbonate compounds such as ethylene carbonate and propylene carbonate can be used as a cocatalyst for promoting the reaction.

  Examples of the foam stabilizer (B) used in the present invention include known silicone surfactants, such as L-5340, L-5420, L-5421, L-5740, L-made by Toray Dow Corning. 580, SZ-1142, SZ-1642, SZ-1605, SZ-1649, SZ-1675, SH-190, SH-192, SH-193, SF-2945F, SF-2940F, SF-2936F, SF-2937F, SRX-294A, Shin-Etsu Chemical F-305, F-341, F-343, F-374, F-345, F-348, Goldschmitt B-8404, B-8407, B-8465, B -8444, B-8467, B-8433, B-8466, B-8870, B-8450 and the like. The amount of (B) used is suitably 0.1 to 5% by weight based on the polyol.

  In the present invention, other additives can be used. Examples of the additives include plasticizers, fillers, colorants, flame retardants, organic or inorganic fillers, antioxidants, ultraviolet absorbers, plasticizers, pigments / dyes, antibacterial agents / antifungal agents, and the like. . In the present invention, it is preferable to use a flame retardant. Examples of the flame retardant include phosphate esters such as triethyl phosphate and tris (β-chloropropyl) phosphate, and phosphate compounds such as phosphite esters such as ethyl phosphite and diethyl phosphite.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these. In Examples and Comparative Examples, “%” indicates “mass%”.

[Synthesis of polyisocyanate for rigid polyurethane foam]
Example 1
98.3 kg of P-MDI (1) was charged into a reactor equipped with a stirrer, a cooling tube, a nitrogen introduction tube, and a thermometer, and heated to 40 ° C. while stirring. Next, 1.7 kg of the modifier (1) was added and reacted at 80 ° C. for 4 hours with stirring to obtain polyisocyanate for rigid polyurethane foam (NCO-1). NCO-1 had an NCO content of 28.7% and a viscosity at 25 ° C. of 1170 mP · s.

Examples 2-8, Comparative Examples 1-3
In the same manner as in Example 1, polyisocyanate compositions NCO-2 to 9 for rigid polyurethane foam were obtained with the raw materials and preparation ratios shown in Tables 1 to 3. NCO-1 to 6 modified with a low molecular weight polyol having a molecular weight of 200 or less containing a side chain methyl group had an appropriate viscosity and did not cause turbidity in appearance. On the other hand, NCO-7 was low in viscosity because it was not able to introduce sufficient urethane groups because the amount of raw material glycol was small. NCO-8 had a high viscosity because the amount of raw material glycol was too large. In addition, NCO-9 modified with a linear low molecular weight polyol was turbid.

Examples 1-6, Comparative Examples 1-3, and Tables 1-2 MR-200: Polymeric MDI manufactured by Nippon Polyurethane Industry
Trade name, Millionate (registered trademark) MR-200
Isocyanate content = 31.1%
MDI content = 40%
Isomer content other than 4,4′-MDI in MDI = 0.1%
Viscosity at 25 ° C. = 130 mPa · s
* Also in Tables 2 and 4, 12PD: 1,2-propanediol 13BD: 1,3-butanediol 2MPD: 2-methyl-1,3-propanediol 3MPD: 3-methyl-1,5-pentanediol DPG: Dipropylene glycol 14BD: 1,4-butanediol

[Formulation of polyol premix]
The polyol premix OH-1 was obtained by mixing at the mass blending ratio shown below.
Polyol-1: 65
Polyol-2: 20
Polyol-3: 15
CAT-1: 1.0
CAT-2: 0.15
CAT-3: 0.1
SUR-1: 1.5
Water: 2.1
Cyclopentane: 15.16

In the above blending example, polyol-1:
Polyether polyol mainly composed of polyether polyol obtained by addition of propylene oxide with sucrose as an initiator, nominal hydroxyl value = 390
Polyol-2:
Polyether polyol mainly composed of polyether polyol obtained by addition of propylene oxide with sorbitol as an initiator, nominal functional group number = 5.0, nominal hydroxyl value = 460
Polyol-3:
Polyether polyol using toluenediamine as an initiator, nominal hydroxyl value = 460
CAT-1:
Amine-based catalyst, trade name “TOYOCAT-TE (manufactured by Tosoh)”
CAT-2:
Amine-based catalyst, trade name “TOYOCAT-TRC (manufactured by Tosoh)”
CAT-3:
Amine-based catalyst, trade name “TOYOCAT-DT (manufactured by Tosoh)”
SUR-1:
Silicone foam stabilizer, trade name "SZ-1725 (manufactured by Dow Corning Toray)"

[Production and evaluation of rigid polyurethane foam]
Examples 7-12, Comparative Examples 4-5
After the isocyanate component shown in Tables 1 and 2 and the polyol component blended above were blended with the isocyanate index 125, the polyol was adjusted to 20 ° C. ± 1 ° C. and the isocyanate was adjusted to 45 ° C. ± 1 ° C. Weigh in a polyethylene beaker, stir and mix for 2 to 5 seconds with a stirring mixer at a rotation speed of 5000 rpm, mold foaming in a 250 x 250 x 50 mm aluminum container inside a 250 x 250 x 50 mm aluminum container set in advance. The density and thermal conductivity of the obtained foam were measured. The results are shown in Tables 3 and 4.
In addition, since the viscosity of isocyanate was too high for NCO-8, actual liquid feeding was difficult, and NCO-9 was not evaluated because of poor appearance.

表３、４より、メチル基を有する低分子ポリオールで変成し、適度な粘度を有するＮＣＯ−１〜６を用いて得られた硬質ポリウレタンフォームは、良好な熱伝導性を示した。しかし、未変成のポリメリックＭＤＩをそのまま用いた比較例４では、特に熱伝導特性が悪いものであった。また、比較例５（ＮＣＯ−７）では、イソシアネートの変成量が少なすぎるため、熱伝導特性が向上したとは言い切れないものであった。

From Tables 3 and 4, the rigid polyurethane foam obtained by using NCO-1 to 6 modified with a low molecular polyol having a methyl group and having an appropriate viscosity showed good thermal conductivity. However, in Comparative Example 4 using the unmodified polymeric MDI as it was, the heat conduction characteristics were particularly poor. In Comparative Example 5 (NCO-7), the amount of isocyanate modification was too small, and it could not be said that the heat conduction characteristics were improved.

Claims (3)

  Contains an isocyanate group-containing prepolymer produced by reacting a polymeric MDI (A1) with a low molecular weight polyol (A2) containing a methyl group and having a molecular weight of 200 or less, and has a viscosity at 25 ° C. of 800 to 2,500 mPa · s. A polyisocyanate composition for rigid polyurethane foam for foaming cyclopentane, characterized in that:   The low molecular polyol (A2) is selected from 1,2-propanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-propanediol, dipropylene glycol The polyisocyanate composition for rigid polyurethane foam for foaming cyclopentane according to claim 1, wherein the composition is a polyisocyanate composition. In the method for producing a rigid polyurethane foam in which a polyisocyanate and a polyol are reacted and foamed in the presence of a catalyst, a foaming agent and a foam stabilizer, the polyisocyanate is the polyisocyanate composition according to claim 1 or 2, A method for producing a rigid polyurethane foam, wherein the agent is used in combination with cyclopentane and water.