JPH0220535A - Production of expanded synthetic resin - Google Patents

Abstract

PURPOSE:To obtain a rigid expanded synthetic resin in good workability without causing any environmental pollution etc., by reacting an active hydrogen compound with a polyisocyanate compound in the presence of a blowing agent comprising a specified azodicarboxylic acid derivative. CONSTITUTION:An active hydrogen compound (A) having at least two active hydrogen functional groups reactive with an isocyanate group e.g., polyether polyol) is reacted with a polyisocyanate compound (B) (e.g., tolylene diisocyanate) in the presence of a blowing agent (C) comprising an azodicarboxylic acid derivative of the formula R1R2NCON=NCONR3R4 (wherein R1, R2, R3 and R4 are each H, a 1-10 C saturated or unsaturated alkyl) (e.g., azobisisobutyramide) to obtain an expanded synthetic resin. An open-cellular rigid urethane foam can be easily produced by using a combination of component C with a low-boiling (halo)hydrocarbon or the like as said blowing agent.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a foamed synthetic resin such as polyurethane foam, and in particular a method for producing a foamed synthetic resin characterized by the use of a specific blowing agent. It is about the method.

[Prior Art] It is widely practiced to produce a foamed synthetic resin by reacting an active hydrogen compound having two or more active hydrogen-containing groups capable of reacting with an isocyanate group with a polyisocyanate compound in the presence of a catalyst and a blowing agent. Examples of active hydrogen compounds include polyhydroxy compounds and polyamine compounds. Examples of foamed synthetic resins that can be obtained include polyurethane foam, polyisocyanurate foam, and polyurea foam. Examples of the foamed synthetic resin include microcellular polyurethane elastomer and microcellular polyurethane urea elastomer.

Although various compounds are known as blowing agents for producing the above-mentioned foamed synthetic resin, trichlorofluoromethane (R-11) is mainly used. Also, usually R-
Water is further used in combination with 11. Furthermore, when foaming is carried out by the froth method etc., dichlorodifluoromethane (R
-12) is used in combination. Furthermore, various proposals have been made that other fluorine-containing halogenated hydrocarbons with relatively low boiling points can be used as blowing agents, but with the exception of the above R-11 and R-12, they are still widely used ( The use of other low boiling point halogenated hydrocarbon blowing agents, such as methylene chloride, has also been proposed in place of the fluorine-containing halogenated hydrocarbon blowing agents.

It is also known to use azodicarboxylic acid as a blowing agent to produce sheets.

(Special Publication No. 62-28480, Special Publication No. 61-55127
(See Publication No.) [Problems to be Solved by the Invention] R-11 and R-12, which have been widely used in the past, generally have low solubility in active hydrogen compounds such as polyols, and phase separation occurs in mixed component systems containing both. This tends to cause problems, and for this reason, there was a problem of narrowing the range of active hydrogen compounds that can be used.When phase separation occurs in a mixed system with an active hydrogen compound, R-11 or R-1, which has a heavy specific gravity,
2 accumulates at the bottom of the storage container, resulting in an inhomogeneous mixed solution, which disrupts the reaction equivalence with the polyisocyanate compound, making it impossible to obtain a normal foam. Even if there is no clear separation into two phases, poor solubility tends to lead to poor mixing with the polyisocyanate compound, residual unreacted components, and generation of rough foam called voids during the production of foams by polymerization and foaming. Furthermore, R-11 and R-12 have the potential to destroy the earth's protective ozone layer through ozone-depleting chain reactions, and there is a desire to reduce their usage.

Furthermore, water, which is widely used as a blowing agent, reacts with isocyanate and therefore has the disadvantage of embrittling the produced foamed synthetic resin.

Furthermore, various proposals have been made for the production of open-cell foamed synthetic resins, but most of them generally involve the mixing of foreign substances such as cell-opening agents, and therefore are not carried out under highly closed-cell conditions, such as It is difficult to obtain open-cell foamed synthetic resins when forming open-cell foams using hard bowls, high-density foams, or mold injection foaming with strong closed system properties. There is a need for the development of a foaming agent that can produce foamed synthetic resins.

[Means for Solving the Problems] In the present invention, in order to solve the above-mentioned problems, an active hydrogen compound having two or more active hydrogen-containing functional groups capable of reacting with an isocyanate group and a polyisocyanate compound are combined in the presence of a blowing agent. In the method for producing a foamed synthetic resin by the reaction described below, azodicarboxylic acids are used as a blowing agent. Examples of this compound include azodicarboxylic acid represented by the general formula % (R, , R2 is an alkyl group having 2 to 8 carbon atoms), its amide, and its ester. Examples of the azodicarboxylic acids include azobisisobutyric acid amide (hereinafter simply referred to as azodicarbonamide), azobisisobutyric acid alkyl ester, and azobisdimethylisovaleric acid alkyl ester, with azodicarbonamide being particularly preferred.

Azodicarboxylic acids are decomposed by the reaction heat generated when polyisocyanate reacts with active hydrogen compounds that have two or more active hydrogen-containing functional groups that can react with isocyanate groups, and generate nitrogen gas, and this nitrogen gas has a foaming effect. will be carried out. The addition ratio of azodicarboxylic acids is 0.1 to 40 wt%, especially 0.5 to 10 wt%, based on the polyol.
t% is appropriate, and a continuous form can be obtained.

In the present invention, the blowing agent is a blowing agent that has a blowing action at a relatively low temperature such as a low-boiling halogenated hydrocarbon, a low-boiling hydrocarbon, an inert gas, or water (hereinafter referred to as a side blowing agent).
It is also possible to use these in combination to obtain extremely favorable results.

Examples of the sub-foaming agent include R-11 and water.

When a sub-foaming agent and a specific compound are used together, the proportion of the specific compound in the blowing agent is suitably 0.5 to 90 wt%, preferably 5 to 60 wt%.

In this way, when an active hydrogen compound and a polyisocyanate compound are reacted in a state where a specific compound and a sub-blowing agent coexist, as the temperature rises due to the reaction heat of this reaction, first stage foaming by the sub-blowing agent occurs. is carried out, and then a second stage foaming is carried out using a specific compound. Then, the walls of the foam formed in the first stage foaming are torn due to the increase in internal pressure due to the second stage foaming, making it particularly easy to obtain a rigid urethane foam having open cells, which has been difficult to obtain in the past. In addition, organic acids such as Lewis acid, oxalic acid, succinic acid, and adipic acid, urea, and urea compounds (hereinafter collectively referred to as additives) can be added in a weight ratio of 0.1 to 10 times the weight of adibiscarboxylic acids. By lowering the decomposition temperature of azodicarboxylic acids, the above effects can be further enhanced.

2 active hydrogen-containing functional groups that can react with isocyanate groups
The active hydrogen compound having the above is a compound having two or more active hydrogen-containing functional groups such as a hydroxyl group or an amino group, or a mixture of two or more such compounds. Particularly preferred are compounds having two or more hydroxyl groups, mixtures thereof, or mixtures containing fir as a main component and further containing polyamine or the like. As the compound having two or more hydroxyl groups, widely used polyols are preferred, but compounds having two or more phenolic hydroxyl groups (eg, phenol resin initial condensate) can also be used. Polyols include polyether polyols, polyester polyols,
Examples include polyhydric alcohols and diethylene polymers containing hydroxyl groups. In particular, it is preferable to use only one or more types of polyether polyols, or to use them as a main component in combination with polyester polyols, polyhydric alcohols, polyamines, alkanolamines, and other active hydrogen compounds. The polyether polyol is preferably a polyether polyol obtained by adding a cyclic ether, particularly an alkylene oxide such as propylene oxide or ethylene oxide, to a polyhydric alcohol, saccharide, alkanolamine, or other initiator. Further, as the polyol, it is also possible to use a polyol composition called a polymer polyol or a graft polyol, in which fine particles of a vinyl polymer are dispersed in a mainly polyether polyol. Polyester polyols include polyhydric alcohols, polycarboxylic acid condensation polyols, and cyclic ester ring-opening polymer polyols. Polyhydric alcohols include ethylene glycol, propylene glycol,
These include diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, pentaerythritol, jetanolamine, and triethanolamine. Compounds having two or more phenolic hydroxyl groups include resol-type initial condensates in which phenols are condensed and bonded with excess formaldehyde in the presence of an alkali catalyst; There are benzylic-type precondensates made by reacting excess phenols with formaldehyde in the presence of an acid catalyst, and novolac-type precondensates. The molecular weight of these initial condensates is preferably 200 to 10,000. Here, phenols mean those in which one or more carbon atoms of the skeleton forming a benzene ring are directly bonded to a hydroxyl group, and also include those having other substituent bonding groups within the same structure. Typical examples include phenol/cresol, bisphenol A, and resorcinol. Further, formaldehydes are not particularly limited, but formalin and paraformaldehyde are preferred. The hydroxyl value of the polyol or the mixture of active hydrogen compounds is often selected from about 20 to 1000 depending on the purpose.

Examples of polyisocyanate compounds include aromatic, alicyclic, or aliphatic polyisocyanates having two or more isocyanate groups, mixtures of two or more thereof, and modified polyisocyanates obtained by modifying them. Specifically, for example, tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenylisocyanate (common name: crude MDI),
Polyisocyanates such as xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate and their prepolymer-type modified products,
There are urea-modified products, urea-modified products, etc.

When reacting active hydrogen compounds and polyisocyanate compounds, the use of catalysts is usually required. As a catalyst,
Metal compound catalysts such as organotin compounds and tertiary amine catalysts such as triethylenediamine are used to promote the reaction between active hydrogen-containing groups and isocyanate groups. Further, a polymerization catalyst that causes isocyanate groups to react with each other, such as a carboxylic acid metal salt, is used depending on the purpose. Furthermore, many foam stabilizers are used to form good bubbles. Examples of foam stabilizers include silicone foam stabilizers and fluorine-containing compound foam stabilizers. Compounding agents that can be used include, for example, fillers, stabilizers, colorants, flame retardants, and the like.

In addition, when using an organic tin compound as a catalyst, since the organic tin compound has a tendency to be deactivated by acid, the first
As the blowing agent, it is desirable to use a salt, especially a tertiary amine salt such as triethylenediamine.

Using these raw materials, polyurethane foam, urethane-modified polyisocyanate foam, microcellular polyurethane elastomer, microcellular polyurethane urea elastomer, microcellular polyurea elastomer, and other foamed synthetic resins can be obtained.

Polyurethane foam can be broadly divided into rigid polyurethane foam, semi-rigid polyurethane foam, and flexible polyurethane foam. The present invention is particularly useful in the production of rigid polyurethane foams, urethane-modified polyisocyanurate foams, and other rigid foams, which are fields in which halogenated hydrocarbon blowing agents are used in large quantities. Among these, it is particularly useful in the production of rigid polyurethane foams obtained by using polyols or polyol mixtures with a hydroxyl group count of 200 to 900 and aromatic polyisocyanate compounds, and it is easy to obtain foams with open cells. I can do it. In addition, the foaming ratio is 5 times or more,
Preferably, it is 10 times or more.

[Function] The blowing agent (azodicarboxylic acids) of the present invention is decomposed by the heat of reaction between the active hydrogen compound and the polysissocyanate compound,
Generates nitrogen gas and performs foaming action. By adding an additive, the decomposition temperature of azodicarboxylic acids is lowered and the above effects are enhanced. Furthermore, by using a sub-valve foaming agent in combination with azodicarboxylic acids, the walls of the foam produced by the sub-valve foaming agent are broken by the increase in internal pressure due to the nitrogen gas generated by decomposition of the specific compound, allowing the bubbles to communicate.

[Example] Example 1 70 parts of a polyether with a hydroxyl value of 350 obtained by adding propylene oxide to sucrose and jetanolamine, 30 parts of a polyether with a hydroxyl value of 400 obtained by adding propylene oxide to glycerin,
Silicone foam stabilizer (Nippon Unicar (product name: Y-682)
7) 1.5 parts, water 2.8 parts, N, N, N', N', N
”-2.0 parts of pentamethyldiethylenetriamine, 1.
4-diazabicyclo[2゜2.21 octentriethylenediamine 0.5 part, azodicarbonamide (Nippon Carbide Industries ■trade name: Azobis CA-51C) 3.0 parts
Add 14 parts of polymethylene polyphenylisocyanate (MD Kasei brand name PAPI 135) to the mixed solution.
Table 1 shows the results of mixing 5 parts at a liquid temperature of 20° C., putting the mixture into a box and mold, foaming it, and evaluating it. The box is made of wood and measures 200mm x 200mm x 200mm.
The mold is made of aluminum and measures 400mm x 400mm
A closed system with a size of 5011101 and having five holes of φ5 mm in the lid was used. The expansion ratio was about 30 times.

[Comparative Example 1] Table 1 shows the results of foaming performed under the same conditions as in Example 1 except that azodicarbonamide was not included.

Table 1 The criteria for judgment are as follows.

○: The foam is uniform and the open cell ratio is 90% or more △: The foam is uneven or the open cell ratio is 75 or more and less than 90% ×: The foam is uneven or the open cell ratio is less than 75% Example 2 Propylene oxide in glycerin Hydroxyl value 3, with 8% by weight of acrylonitrile polymer dispersed in
100 parts of polyether No. 2, jetanolamine 1.0
1 part, 3.0 parts of water, 2.0 parts of silicone foam stabilizer (Toray Silicone (Flesh product name 5F-2962), 0.4 part of 1,4-diazabicyclo[2,2,2]octentriethylenediamine, N, N,N',N'-tetramethylhexamethylenediamine 0.4 part, azodicarbonamide (Nippon Carbide Industries ■Product name: Azobis CA-5IC)
Toluene diisocyanate (
2.4 bodies = 2.6 bodies 80:20) 24 parts at a liquid temperature of 25
Table 2 shows the results of mixing the mixture at ℃ and putting it into a box and mold for foaming and evaluation. The box is made of wood and is 300mm long.
X 300 n+IIIX 300 mm, mold made of aluminum 350 mm X 350 mm X 100 m
A closed system with a size of m, and a lid having five holes of φ3 mm was used. The expansion ratio was about 15 times.

[Comparative Example 2] Table 2 shows the results of foaming performed under the same conditions as in Example 2 except that azodicarbonamide was not included.

Table 2 [Effects of the Invention] When the blowing agent of the present invention is used, foaming is performed with nitrogen gas, which eliminates the problems caused by conventional sub-foaming agents, and allows the use of the blowing agent and sub-foaming agents together. As a result, the amount of the sub-foaming agent used can be reduced, the problems caused by the use of the sub-foaming agent can be solved, and a hard foamed synthetic resin having open cells can be obtained.

Claims (1)

[Claims] 1. In the production of a foamed synthetic resin by reacting an active hydrogen compound having two or more active hydrogen-containing functional groups capable of reacting with an isocyanate group with a polyisocyanate compound in the presence of a foaming agent, There are azodicarboxylic acids▲mathematical formulas, chemical formulas, tables, etc.▼ (R_1, R_2, R_3, R_4 are hydrogen or carbon number 1
-10 saturated or unsaturated alkyl groups). 2. The amount of azodicarboxylic acids used is 0.1 of the polyol.
The manufacturing method according to claim 1, wherein the amount is 40 wt%. 3. Claim 1 or 2, wherein the foamed synthetic resin has open cells.
Manufacturing method described. 4. React with azodicarboxylic acids, Lewis acids, organic acids,
4. The method according to claim 1, wherein the method is carried out in the presence of urea or a urea compound. 5. The manufacturing method according to claim 1, 2, 3 or 4, wherein azodicarboxylic acids and a low-boiling halogenated hydrocarbon, a low-boiling hydrocarbon, and water as the active gas are used together as the blowing agent. 6. The proportion of azodicarboxylic acids included in the blowing agent is 0.
The manufacturing method according to claim 5, wherein the amount is 5 to 60 wt%.