JPH03149213A - Production of synthetic resin foam - Google Patents

Abstract

PURPOSE:To produce a synthetic resin foam while effectively reducing the amt. used of a chlorofluorohydrocarbon blowing agent which might deplete the ozone layer by reacting a polyisocyanate with active hydrogen compds. contg. at least two active hydrogen groups in the presence of water as a blowing agent. CONSTITUTION:An active hydrogen compd. having at least two isocyanate- reactive active hydrogen groups such as hydroxyl or amino groups, or a mixture of two or more of such active hydrogen compds. is reacted with a polyisocyanate having, on an average, at least 2.5 isocyanate groups in the molecule in the presence of water, as a blowing agent, in an amt. of 4wt.% based on the total active hydrogen compds. As the active hydrogen compd, one contg. two or more hydroxyl groups is pref. and so is a mixture of two or more of such compds. or a mixture mainly comprising such compds. and contg. a polyamine, etc.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for producing a foamed synthetic resin such as a 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. ing. Examples of active hydrogen compounds include polyhydroxy compounds and polyamine compounds. Examples of the resulting foamed synthetic resin include polyurethane foam, polyisocyanurate foam, and polyurea foam. In addition, examples of foamed synthetic resins with relatively low foaming 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-ll) 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. Various proposals have been made that other relatively low-boiling chlorinated fluorinated hydrocarbons can be used as blowing agents;
With the exception of ll and R-12, they have not yet come into widespread use. It has also been proposed to use other low boiling point halogenated hydrocarbon blowing agents, such as methylene chloride, in place of the chlorinated fluorinated hydrocarbon blowing agents.

[Problem to be solved by the invention] Chlorinated fluorinated hydrocarbons that are extremely stable in the atmosphere, such as R-ll and R-12, which have been widely used in the past, reach the ozone layer above the atmospheric layer without being decomposed. Therefore, it was thought that it would be decomposed by the effects of ultraviolet rays, etc., and that the decomposed products could destroy the ozone layer. Chlorinated fluorinated hydrocarbons such as those mentioned above used as blowing agents,
Because some of it leaks into the atmosphere, there are concerns that its use could be part of the cause of ozone layer depletion.

As a method of solving the above problem, it has been proposed to use a large amount of water as a blowing agent. Water is the main blowing agent in flexible polyurethane foams and an important secondary blowing agent in rigid polyurethane foams. However, it is difficult to use them in high enough proportions to replace the fluorinated chlorinated hydrocarbons currently used as the main blowing agents for rigid polyurethane foams. Water is a reactive blowing agent and reacts with the isocyanate to form urea bonds. Foamed synthetic resins containing many urea bonds tend to be more brittle than foamed synthetic resins containing more urethane bonds produced by the reaction between a polyol and an isocyanate compound. Furthermore, water has a different reactivity than active hydrogen compounds such as polyols. When foaming with water is performed, the start-up of the reaction is delayed compared to when a conventional fluorinated chlorinated hydrocarbon is used as a foaming agent, and the reaction tends to proceed rapidly in the latter half. These phenomena cause problems in rigid polyurethane foams, such as significant embrittlement, deterioration in strength, and deterioration in adhesive properties; . The use of water as a blowing agent to replace conventional fluorinated chlorinated hydrocarbon blowing agents requires the development of technology that overcomes these problems.

[Means for Solving the Problems] The present invention provides the following inventions that have been made to solve the above-mentioned problems.

2 active hydrogen-containing reactive groups that can react with isocyanate groups
In the method of producing a rigid foam by reacting the active hydrogen compound having the above with a polyisocyanate compound in the presence of a blowing agent, 4 parts by weight or more of water is used as a blowing agent based on the total active hydrogen compound, and one molecule of water is used as a blowing agent. A method for producing a foamed synthetic resin, comprising using a polyisocyanate compound having an average of 2.5 or more isocyanate groups therein.

The method for producing a foamed synthetic resin according to the present invention is characterized in that a large amount of water is used and an isocyanate having a high number of functional groups is used to increase the strength of the foam. In normal rigid urethane foam, the deterioration of the resin of the foam due to the use of water as a blowing agent is as follows: Polyol, which has an average number of functional groups of about 3 to 4, water, which has an average number of functional groups of 2, and crude, which has an average number of functional groups of 3 or less. It is thought that the MDI is increasing and the crosslinking density of the resin is decreasing. As a result of intensive studies by the present inventors, it has been found that there is a limit to increasing the number of functional groups by changing the polyol, and it is necessary to increase the number of functional groups in the isocyanate. The polyisocyanate compound in the present invention has a functional group number of 2.5 or more, preferably 2.7.
above, more preferably 3 or more. It is preferable that the total amount of the polyisocyanate compound used has a high number of functional groups, but an improvement effect can also be seen by using it partially. At this time, it is preferable that the polyisocyanate having a high number of functional groups exceeds 20% by weight based on the total polyisocyanate compound.

In the technique of the present invention, water can of course be used alone as a blowing agent, but it can also be used in combination with other blowing agents. Examples of blowing agents that can be used in combination include the current blowing agents R-ll, R-12°R-123, and R-141b%R-
134a, other low-boiling halogenated hydrocarbons, low-boiling hydrocarbons, and inert gases. R-ll and R-12
Although there is a risk of depletion of the ozone layer by itself, it is possible to reduce the amount of water used as a blowing agent by increasing the amount of water used.

Other low-boiling halogenated hydrocarbons include:

There are halogenated hydrocarbons that do not contain fluorine atoms, such as methylene chloride, and fluorine-containing halogenated hydrocarbons other than those mentioned above. Low-boiling hydrocarbons include butane, hexane, and pentane, and inert gases include air and nitrogen.

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 (for example, 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. As the polyether polyol, 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 nitrate is preferred. 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 alcohol-polycarboxylic acid condensation polyols and cyclic ester ring-opening polymer polyols, and polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerin, and trivalent alcohols. Examples include methylolpropane, 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 compound hydrogen is about 100 to 800, especially 20
It is often selected from 0 to 600 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. be.

In the present invention, the average number of isocyanate groups per molecule of the polyisocyanate compound must be 2.5 or more, preferably 2.5 to 4, particularly 2.5 to 3.5.

Preferably, an aromatic polyisocyanate compound is used, such as polymethylene polyphenylisocyanate (commonly known as crude MDI) having the above-mentioned number of isocyanate groups, tolylene diisocyanate or diphenylmethane diisocyanate modified with a polyol having an average functionality of 2.5 or more,
Modified tolylene diisocyanate, diphenylmethane diisocyanate, etc. having a functional average of 2.5 or more are used. Further, a mixture of these polyisocyanate compounds and a polyisocyanate compound having an average functional group number of less than 2.5 can also be used as long as the average functional group number of the mixture is 2.5 or more. Preferably, polymethylene polyphenylisocyanate, modified diphenylmethane diisocyanate, or at least one and two thereof.
．． Less than 5 functional (modified) tolylene diisocyanate, (
At least one of (modified) diphenylmethane diisocyanate or polymethylene polyphenylisocyanate
Polyisocyanates are used which are mixtures with seeds and have an average functionality of 2.5 to 3.5. The isocyanate group content is not particularly limited, but is 15% by weight.
Above, 20% by weight or more is particularly preferable.

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, foam stabilizers are often used to form good foam. Examples of the foam stabilizer include silicone thread foam stabilizers and fluorine-containing compound foam stabilizers. Other optional additives include fillers, stabilizers, colorants, flame retardants, and the like.

Using these raw materials, polyurethane foam, urethane-modified polyisocyanerate foam, polyurea foam, and other rigid foams can be obtained.

Among these, the present invention is particularly useful in the production of rigid polyurethane foams obtained using polyols or polyol mixtures having a hydroxyl value of about 200 to 600 and aromatic polyisocyanate compounds. When producing these rigid foams, in the present invention, the amount of the blowing agent made of a low-boiling organic compound to be used is preferably θ to 100% by weight, particularly 10 to 40% by weight, based on the active hydrogen compound. At the same time, it is preferred to use at least 4% by weight, preferably from 4 to 10% by weight, especially from 4 to 8% by weight of water, based on the active hydrogen compound.

Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is limited to these Examples [Example] The blowing agent of the present invention for flexible polyurethane foam was evaluated as follows. Ta. The polyols used are as follows.

1) Polyol A: A polyol with a hydroxyl value of 340 made by reacting methane luenediamine with propylene oxide and ethylene oxide.

2) Polyol B: Hydroxyl value 35 obtained by reacting shake rose with monoethanolamine and propylene oxide
0 polyol.

The polyisocyanate compounds used are as follows.

1) Isocyanate A; average number of functional groups 2.4 Crude M
DI 2) Isocyanate B: Average number of functional groups 2. Fukuroud M
DI foaming evaluation was performed as follows. 40 parts by weight of polyol A and 60 parts by weight of polyol B (total of 100 parts by weight of polyol), 2 parts of silicone foam stabilizer, 6 parts of water, and the necessary amount of N,N-dimethylcyclohexylamine as a catalyst to give a gel time of 45 seconds. , R-ll in the necessary amount to make the core density of the foam 30 ± 1 kg/m'', mixed at the above crude MDI liquid temperature of 20°C,
It was put into a wooden box of 0 ma + × 200-m × 200 mm, and was foamed and evaluated.

As a comparative example, a product without using the polyisocyanate of the present invention was foamed. The evaluation criteria are as follows.

The results are shown in Table 1.

<Shape/shape stability of foam> ■ l Dimensional stability ■ Compressive strength 10 No shrinkage is observed Good [Effect] The present invention can effectively reduce the usage amount of chlorinated fluorinated hydrocarbons such as R-ll, which may cause ozone layer depletion, and can produce a foamed synthetic resin with good properties. It is.

Claims (1)

[Claims] 1. In a method for producing a rigid foam by reacting an active hydrogen compound having two or more active hydrogen-containing reactive groups capable of reacting with an isocyanate group with a polyisocyanate compound in the presence of a blowing agent, water is used as the blowing agent at full activation. 1. A method for producing a foamed synthetic resin, which comprises using a polyisocyanate compound containing 4 parts by weight or more based on the hydrogen compound and having an average of 2.5 or more isocyanate groups per molecule.