JPH0220532A - Production of expanded synthetic resin - Google Patents

Abstract

PURPOSE:To advantageously obtain an open-cellular rigid expanded synthetic resin in good workability by reacting an active hydrogen compound with a polyisocyanate compound in the presence of a specified mixed blowing agent comprising a plurality of blowing agents. 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 cyanoacetic acid (derivative or salt), a low-boiling halo-hydrocarbon (e.g., trichlorofuloromethane), a low-boiling hydrocarbon (e.g., butane) and an inert gas or water. In this way, an open-cellular expanded synthetic resin (e.g., rigid urethane foam) can be obtained. The amount of the cyanoacetic acid in the blowing agent is suitably 0.1-50wt.%.

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 R-11 and R-12 mentioned above, they are still widely used. It has not yet reached the point where it will be done. Furthermore, the use of other low-boiling point halogenated hydrocarbon blowing agents such as methylene chloride in place of the fluorine-containing halogenated hydrocarbon blowing agents has also been proposed.

It has also been suggested that cyanoacetic acid be used as a blowing agent.

[Problem 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 a mixed component system containing both tends to cause phase separation problems. (
Therefore, there was a problem in that the range of usable active hydrogen compounds was limited. When phase separation occurs in a mixed system with an active hydrogen compound, R-11 or R-1 with heavy specific gravity
2 accumulates at the bottom of the storage container and becomes a non-homogeneous mixed solution, which disrupts the reaction equivalence with the boisocyanate compound, making it impossible to obtain normal R-envelops. 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 regarding the manufacturing method of open-cell foamed synthetic resins, but most of them generally involve the mixing of foreign substances such as the open-cell rule, so they cannot be produced under conditions of high closed-cell properties, such as hard foams. It is difficult to obtain open-cell foamed synthetic resins when using polyols for open-cell foams, high-density foams, or mold injection foaming that has strong closed system properties. Therefore, there is a demand for the development of a blowing agent that can produce open-cell foamed synthetic resin even under the above conditions.

[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 inocyanate groups and a polyisocyanate compound are used as a blowing agent. In the method of producing a foamed synthetic resin by reacting in the presence of a foaming agent, cyanoacetic acid, a cyanoacetic acid derivative, or a salt thereof is used in combination with a low-boiling halogenated hydrocarbon, a low-boiling hydrocarbon, an inert gas, or water as a blowing agent. .

Next, the present invention will be explained in more detail.

In the present invention, cyanoacetic acid (N
cyanoacetic acid derivatives (hereinafter collectively referred to as cyanoacetic acid, etc.), such as CCH, C00H) or its alkyl esters,
Alternatively, a salt thereof (hereinafter collectively referred to as cyanoacetate etc.) is used.

As cyanoacetic acid, cyanoacetic acid is particularly preferred.

In addition, as cyanoacetic acid etc., -2 secondary and tertiary amine salts, alkali metal salts, alkaline earth metal salts, and transition metal salts can be used, but in particular, the general formula R, R2NH (R1 and R2 are H or the number of carbon atoms) 1 to 15 saturated or unsaturated aliphatic hydrocarbons,
Alternatively, it is represented by a hydrocarbon group including ON, an ether group, a carbonyl group, a cyano group, a cyano group, or a phenyl group (the hydrocarbon group is preferably a saturated or unsaturated aliphatic hydrocarbon having 1 to 15 carbon atoms) Amine salts are preferred.

The first foaming agent decomposes at about 130 to 160° C. due to the heat of reaction between the active hydrogen compound and the polyisocyanate compound to generate carbon dioxide gas, which causes foaming.

The second blowing agent is a low-boiling halogenated hydrocarbon or a low-boiling hydrocarbon.

Use inert gas and water. Examples of the second blowing agent include chlorinated methane, R-11, R-12, butane, hexane, air, nitrogen, and water.

In the present invention, the first blowing agent and the second blowing agent described above are used together. The proportion of the first blowing agent in the blowing agent is
A suitable content is 0.1 to 50 wt%, preferably 1 to 30 wt%.

In the present invention, in the presence of a blowing agent (hereinafter referred to as the present blowing agent) containing the above-described first blowing agent and second blowing agent,
2 active hydrogen-containing functional groups that can react with isocyanate groups
A foamed synthetic resin is produced by reacting the above-mentioned active hydrogen compound with a polyisocyanate compound. At this time, since the second foaming agent has a foaming effect at a relatively low temperature, as the temperature rises due to the heat of reaction, First, first-stage foaming is performed using a second foaming agent, and then second-stage foaming is performed using carbon dioxide gas generated from the first foaming agent. And the first
The walls of the foam formed by stage foaming are ruptured by the increase in internal pressure caused by the second stage foaming, and a continuous foam is obtained.

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 the same as the 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 incyanate 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),
Examples include polyisocyanates such as xylylene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate, as well as prepolymer-type modified products, nurate-modified products, and urea-modified products thereof.

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, which promote the reaction between active hydrogen-containing groups and incyanate groups. Further, a polymerization catalyst that causes incyanate groups to react with each other, such as a carboxylic acid metal salt, is used depending on the purpose. Furthermore, foam stabilizers are often used to form good foam. Examples of the foam stabilizer include silicone foam stabilizers and fluorine-containing compound foam stabilizers. Other optional additives include 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 having a hydroxyl value 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,
9, which is preferably 10 times or more, is desirable.

[Operation] By using a first foaming agent and a second foaming agent together as foaming agents (performing foaming in two stages), the wall of the foam formed in the first stage foaming can be expanded in the second stage foaming. A foamed synthetic resin with broken open cells is obtained. In addition, by using the first blowing agent in combination,
The amount of the second blowing agent used is reduced, and the problems of the prior art due to the use of the second blowing agent are solved.

[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-6827
) 1.5 parts, 348 parts of water, N, N, N', N', N
”-2.0 parts of pentamethyldiethylenetriamine, 1.
Add 145 parts of polymethylene polyphenylisocyanate (MD Kasei ■trade name: PAPI 135) to a mixture of 0.5 parts of 4-diazabicyclo[2゜2.21 octent triethylenediamine and 1.2 parts of cyanoacetic acid at a liquid temperature of 20%.
Table 1 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 200mm long.
The size of the mold was 200 mm x 200 mm, and the mold was made of aluminum and had a size of 400 mm + 400 mm x 50 mm, a closed system, and a lid with 5 holes of 5 mm in diameter. The expansion ratio was about 30 times.

[Comparative Example 1] Table 1 shows the results of foaming under the same conditions as in Example 1 except that cyanoacetic acid 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 Δ: 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
3.0 parts of water, 20 parts of silicone foam stabilizer (Toray Silicone Trade Name 5F-2962), 0.1 parts of 1,4-diazabicyclo[2,2,2]octentriethylenediamine.
Triene diisocyanate (2,4 body: 2.'6
Table 2 shows the results of the evaluation after mixing 24 parts (80:20) at a liquid temperature of 25° C. and putting the mixture into a box and mold for foaming. The box is made of wood and measures 300mm x 3001a.
+X 300mm, the mold is made of aluminum and is 350mm
A closed system with a size of 350 mm x 100 mm and a lid with 5 holes of φ3 mm was used. The expansion ratio was about 15 times.

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

Table 2 [Effects of the Invention] The amount of the second blowing agent used is reduced, the problems caused by the use of the second blowing agent are solved, and a hard foamed synthetic resin having open cells can be obtained.

Claims (1)

[Claims] 1. A method for producing 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 blowing agent, As a blowing agent, cyanoacetic acid, a cyanoacetic acid derivative or a salt thereof;
A method for producing a foamed synthetic resin, which comprises using a low boiling point halogenated hydrocarbon, a low boiling point hydrocarbon, an inert gas, or water in combination. 2. The method according to claim 1, wherein the proportion of cyanoacetic acid, cyanoacetic acid derivatives, or salts thereof in the blowing agent is 0.1 to 50 wt%. 3. Foaming is a low-temperature first stage foaming using a low-boiling halogenated hydrocarbon, a low-boiling hydrocarbon, an inert gas, or water;
3. The method according to claim 1, further comprising a second stage of foaming at a high temperature using cyanoacetic acid, a cyanoacetic acid derivative, or a salt thereof. 4. Cyanoacetate has the general formula R_1R_2N
Claim 1: H (R_1 and R_2 are H or a saturated or unsaturated hydrocarbon having 1 to 15 carbon atoms, or a hydrocarbon group containing OH, an ether group, a carbonyl group, a cyano group, or a phenyl group) amine salt , 2 or 3. 5. The method according to claim 1, 2, 3 or 4, wherein the foamed synthetic resin is a rigid urethane foam having open cells.