JPH08100041A - Production of modified polyisocyanurate foam - Google Patents

Abstract

PURPOSE: To obtain a polyisocyanurate foam having good appearance, closed-cell content, heat resistance, and tumbling friability while using carbon dioxide generated by reaction as the blowing agent. CONSTITUTION: In a process for producing a modified polyisocyanurate foam from a polyisocyanate, a tetracarboxylic dianhydride, a cell stabilizer. and a catalyst, a combination of N,N',N"-tris (dimethylaminopropyl)-s- hexahydrotriazine with an alkali metal chelate is used as the catalyst and the polyisocyanate is mixed with the dianhydride in an equivalent ratio of isocyanate groups to acid anhydride groups of of 3-50.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a modified polyisocyanurate foam. More specifically, it relates to a method for producing a rigid foam using carbon dioxide generated by the reaction as a blowing agent.

[0002]

2. Description of the Related Art Polyisocyanurate foams have been used as heat-resistant foams in the construction and the like. This foam is made of polyisocyanate such as polyphenyl polymethylene polyisocyanate, modifier such as polyether polyol, foam stabilizer such as modified polysiloxane, foaming agent such as halogen-substituted aliphatic hydrocarbon, and cyclization of isocyanate group. It is produced by mixing a catalyst that acts on the trimerization reaction.
Examples of halogen-substituted aliphatic hydrocarbons include aliphatic hydrocarbons (CF) in which all hydrogen is halogen-substituted.
C) such as monofluorotrichloromethane, dichlorodifluoromethane, 1,1-dichlorofluoroethane, and 1,1,2-trichloro-1,2,2-trifluoroethane have been used. However, these halogen-substituted hydrocarbons destroy the ozone layer and cannot be used in the future. As an alternative, some hydrogen has been replaced (H
CFC) or those substituted with only fluorine (HFC, perfluorocarbon, etc.) are being investigated, but problems such as safety and the greenhouse effect have been raised.

[0003]

As a safer foaming agent, it has been studied to use carbon dioxide generated by the reaction of NCO groups with water. However, in the case of rigid foam, the cell structure becomes rough by adding water, and a sufficient heat insulating effect is not obtained. The present inventors have conducted extensive studies to use carbon dioxide as a blowing agent when producing a polyisocyanurate foam. NCO groups are known to release carbon dioxide by various reactions. The present inventors have focused on, as one of the reactions, a reaction in which carbon dioxide and an imide bond are formed from an NCO group and an acid anhydride. However, the reaction between the NCO group and the acid anhydride is 18
It was difficult to form a foam because a high temperature of 0 ° C. or higher and a long reaction time were required. As a technique for solving this problem, there is a technique described in JP-A-63-165422. This technique uses dimethylaminomethylphenol alone as a trimerization catalyst. By using this catalyst alone, the raw materials are mixed, put in a microwave oven, heated for 30 seconds, and then cured in a furnace at 100 ° C. for 10 minutes to obtain a product.

[Means for Solving Problems]

The present inventors have investigated a catalyst system which can be cured at a low temperature in a short time by using an ordinary heating furnace instead of a special heating device such as a microwave oven. As a result, by using a conventional amine-based catalyst in combination with an alkali metal chelate as a cocatalyst, it is possible to promote the reaction between the isocyanate group and the acid anhydride even at a relatively low temperature,
The inventors have found that the obtained modified isocyanurate foam has a good cell structure, and completed the invention.

That is, the present invention relates to a polyisocyanate,
(A) N, N ′, N ″ -tris (dimethylaminopropyl) -s-hexahydrotriazine as a catalyst in the production of a modified polyisocyanurate foam comprising tetracarboxylic dianhydride, a foam stabilizer and a catalyst, and (B) A method for producing a modified polyisocyanurate foam, which comprises using an alkali metal chelate in combination, wherein the polyisocyanate and the tetracarboxylic dianhydride are contained in a functional equivalent ratio of 3 to 50. The present invention also provides a method for producing the modified polyisocyanurate foam, which is characterized in that the mixture is mixed at a ratio of.

The N, N ', N "-tris (dimethylaminopropyl) -s-hexahydrotriazine used in the present invention has hitherto been generally known as an isocyanurate-forming catalyst and is commercially available. Also in the above, commercially available products such as Toyocat TRC (manufactured by Tosoh Corporation), Polycat-41 (Air Product)
Manufactured) can be used. This catalyst is used in an amount of 0.2 to 8 parts by weight, preferably 1 to 6 parts by weight, based on 100 parts by weight of the total amount of polyisocyanate and tetracarboxylic dianhydride. If it is less than 0.2 parts by weight, a sufficient catalytic effect cannot be obtained, and use of more than 8 parts by weight is wasteful.
An abnormal heat generation occurs during the reaction, which is not preferable.

The alkali metal chelate used in the present invention is synthesized by reacting an alkali metal or its hydroxide with a diketone or an aldehyde. Examples of the alkali metal or hydroxide thereof include lithium, sodium, potassium, lithium hydroxide, sodium hydroxide and potassium hydroxide. Examples of the diketone or aldehyde include acetylacetone and salicylaldehyde. Alkali metal chelates are synthesized with them in anhydrous ethyl alcohol.
Since the obtained chelate is a white solid, it is used by dissolving it in ethylene glycol at a ratio of 33% by weight. This catalyst is used in an amount of 0.1 to 8 parts by weight, preferably 1 to 4 parts by weight, based on 100 parts by weight of the total amount of polyisocyanate and tetracarboxylic dianhydride. If it is less than 0.1 part by weight, the effect of the catalyst is not observed. On the other hand, if it is used in an amount of 8 parts by weight or more, a side reaction occurs, which is not preferable.

The weight ratio of N, N ', N "-tris (dimethylaminopropyl) -s-hexahydrotriazine to the alkali metal chelate is preferably 5: 1 to 1: 5, more preferably 3: 1. ~ 1: 3.

When N, N ', N "-tris (dimethylaminopropyl) -s-hexahydrotriazine is combined with an alkali metal chelate, a foam having a good cell structure can be obtained by using these two catalysts. Is believed to form a highly active complex and promote the reaction between the isocyanate group and the acid anhydride.

The polyisocyanate used in the present invention has at least two NCO groups in its molecule. Specifically, polymethylene polyphenyl polyisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4 Examples thereof include'-diphenylmethane diisocyanate and a mixture thereof, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and a mixture thereof, hexamethylene diisocyanate and the like. Modified products of these polyisocyanates such as isocyanurates, alohanates, burettes, and uretonimines can also be used. Further, these can be used in combination of two or more.

The tetracarboxylic acid dianhydride used in the present invention has two acid anhydride groups in its molecule, specifically, benzophenone-3,3 ', 4,4'.
-Tetracarboxylic acid dianhydride, pyromellitic dianhydride, trimellitic anhydride ester of ethylene glycol, trimellitic anhydride ester of glycerin and the like can be mentioned, and these can be used alone or in combination of two or more. Preferably, benzophenone-3,3 ',
4,4'-tetracarboxylic dianhydride, pyromellitic dianhydride, or a mixture thereof.

As the foaming gas used in the present invention, carbon dioxide generated from the reaction between isocyanate and carboxylic acid anhydride is used. Although carbon dioxide generated from this reaction alone can give a foam having a density of up to about 30 kg / m ³ , if a foam having a lower density is desired, or if the amount of carboxylic acid anhydride used is reduced, In addition, if a foam having a low density is desired, another foaming agent such as water or an organic solvent having an appropriate boiling point may be added.

The polyisocyanate and the tetracarboxylic dianhydride are mixed such that the equivalent ratio of the functional groups is 3 to 50. Since the imide group is obtained by the reaction of 1 equivalent of NCO group and 1 equivalent of acid anhydride group, in order to obtain a polyisocyanurate foam containing an imide group, it is necessary to mix them so that the equivalent ratio exceeds 1. If the equivalent ratio is less than 1, the mixing viscosity of the polyisocyanate and the tetracarboxylic dianhydride becomes high, and uniform mixing and reaction cannot be achieved. Further, the amount of carbon dioxide generated is too large, and a foam having a good cell structure cannot be obtained. On the other hand, when the equivalent ratio exceeds 50, the amount of carbon dioxide generated is small and the foam density is high. In addition, the foam becomes brittle and cannot be put to practical use. More preferably 3 to 30
Are mixed in an equivalent ratio of.

Examples of the foam stabilizer used in the present invention include silicone foam stabilizers used in the production of polyurethane foams. The structure of this silicon-based foam stabilizer is a polydimethylsiloxane / polyalkylene copolymer, and commercially available products are DC-193 and DC manufactured by Dow Corning.
-197 and so on.

In the modified polyisocyanurate foam of the present invention, the above polyisocyanate and tetracarboxylic dianhydride are mixed in a predetermined ratio, and a foam stabilizer is further added to the modified polyisocyanurate foam. It is obtained by reacting. A moderate reaction rate can be obtained by heating the mixture to 50 to 150 ° C., preferably 100 to 120 ° C.

In the modified polyisocyanurate foam of the present invention, an imide bond is formed after carbon dioxide is released by the reaction between the NCO group and the acid anhydride. Since the imide bond has a high thermal decomposition temperature and the cross-linking density in the foam is low due to modification, the resulting modified polyisocyanurate foam has excellent heat resistance and good cancer resistance (foam powder drop by contact or friction). Less property (Tumbli
It also has the secondary effect of having ng Friability).

[0017]

According to the present invention, a foam can be obtained at an appropriate curing speed without using a special heating device such as a microwave oven. Further, an epoch-making polyisocyanurate foam having a good appearance, a closed cell ratio, heat resistance and easy cancer can be produced without using a foaming agent.

The examples and comparative examples will be described in more detail below. "Parts" in these examples means "parts by weight" unless otherwise specified. The present invention is not limited to these examples. Example 1 Polymethylene polyphenyl polyisocyanate (Millionate MR-300, manufactured by Nippon Polyurethane Industry Co., Ltd.,
Abbreviated as MR-300. ) 100 parts, benzophenone-
3,3 ', 4,4'-Tetracarboxylic acid dianhydride (BT
DA) 40 parts (equivalent ratio 3) and DC-1 as a foam stabilizer
A 33 wt% ethylene glycol solution (AA of Toyocat TRC and potassium acetylacetone) as a catalyst in a mixture of 3 parts of 97 (manufactured by Dow Corning) (AA
-K) 3 parts each (use the liquid temperature adjusted to 23 ± 1 ° C).
The same applies to the following Examples and Comparative Examples), and after stirring for 10 seconds,
It was poured into an open mold and reacted in an oven at 120 ° C. to obtain a foam. Example 2 100 parts MR-300, 6 parts BTDA (equivalent ratio 2
0) and a mixture of 2 parts of DC-197, Toy
2 parts each of ocat TRC and AA-K were blended and 10
After stirring for seconds, the mixture was poured into an open mold and reacted in an oven at 120 ° C. to obtain a foam.

Comparative Example 1 MR-300 and DC-197 in the same amount as in Example 1 were mixed with 15 parts of HCFC-141b as a foaming agent, and Toyocat TRC as a catalyst was added in the same amount as in Example 1 for 10 seconds. After stirring, the mixture was poured into an open mold and reacted at room temperature to obtain a foam. Comparative Example 2 The same amount of MR-300 and DC-197 as in Example 1 was mixed with 7 parts of water as a foaming agent, and Toy was used as a catalyst.
Ocat TRC was added in the same amount as in Example 1, stirred for 10 seconds, poured into an open mold, and reacted at room temperature to obtain a foam. Comparative Example 3 MR-300, BTDA, and DC in the same amounts as in Example 1
-197 was mixed, and Toyocat was used as a catalyst.
The same amount of TRC as in Example 1 was added, the mixture was stirred for 10 seconds, allowed to flow in an open mold, and reacted in an oven at 120 ° C to obtain a foam. Comparative Example 4 MR-300, BTDA, and DC in the same amounts as in Example 1
-197 was mixed, and as a catalyst, 3 parts of dimethylaminomethylphenol (DMP-30) and 3 parts of AA-K were added, and after stirring for 10 seconds, the mixture was allowed to flow in an open type at 120 ° C.
Was reacted in an oven to obtain a foam.

<Appearance of foam, evaluation method of physical properties> The obtained foam was observed in appearance and subjected to a flame resistance test (ASTM D 30).
14), smoke density measurement (ASTM D 2843), easy cancer test (ASTM C 421), density measurement (JI
S A 9514) and closed cell ratio measurement (ASTM D
2856). The flame resistance test was evaluated by the weight residual rate after combustion. The smoke emission test smoke was evaluated by the light attenuation rate at 100 seconds after the start of combustion, and the smoke density was 90% or more, the smoke density was high, 60 to 90% was medium density, and 60% or less was low density. The Raku cancer test was evaluated by the weight loss rate after the test.

As shown in Table 1, in Examples, foams having a good appearance and a closed cell ratio were obtained without using a foaming agent. In addition, epoch-making polyisocyanurate foams having good heat resistance and easy cancer resistance were obtained.

[0022]

[Table 1]

[0023]

[Table 2]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08G 101: 00) C08L 75:04

Claims (2)

[Claims] 1. In the production of a modified polyisocyanurate foam comprising a polyisocyanate, a tetracarboxylic dianhydride, a foam stabilizer and a catalyst, the catalyst (A) is used as the catalyst.
N, N ', N "-tris (dimethylaminopropyl)-
characterized in that s-hexahydrotriazine and (B) an alkali metal chelate are used in combination,
A method for producing a modified polyisocyanurate foam. 2. The modified polyisocyanurate foam according to claim 1, wherein the polyisocyanate and the tetracarboxylic dianhydride are mixed in a functional equivalent ratio of 3 to 50. Method.