JPH0959409A - Production of polyurethane foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyurethane foam having excellent surface properties and a low density within a short demolding time. SOLUTION: This process for producing a microcellular polyurethane foam having a density of 0.2-0.8g/cm<3> from a mixture comprising a polyol, a catalyst, a blowing agent, a crosslinking agent and optionally an internal mold release, a reinforcement and other adjuvants by a reaction injection molding process, wherein the blowing agent is an adduct of an amine compound having a prim. or sec. amino group with carbon dioxide, the water content of the polyol mixture is 0.8wt.% or below, and the amount of the crosslinking agent used is 20-1,000 pts.wt. per 100 pts.wt. polyol, is provided.

Description

Detailed Description of the Invention

[0001]

The present invention has a density of 0.2 to 0.8 g.
The present invention relates to a method for efficiently producing a polyurethane foam having fine cells / cm ³ by a reaction injection molding method in a short time, and the polyurethane foam having such fine cells is used for an interior trim of an automobile, for example, Used as a door trim and backup material for consoles.

[0002]

BACKGROUND OF THE INVENTION Polyurethane foams contain at least 2 hydrogens reactive with polyisocyanates and isocyanate groups.
To a compound (hereinafter referred to as a polyol) contained therein, a catalyst, etc., as a foaming agent, is added water such as carbon dioxide that reacts with a CFC hydrocarbon or polyisocyanate. Is introduced into a mold that can be sealed. Raw materials are
It is expanded and expanded in the mold and then cured to be taken out as a polyurethane foam. The mold is made of a material having a high thermal conductivity in order to control the reaction temperature, and a metal mold (hereinafter referred to as a mold) or a resin mold is generally used. The density of the resulting foam is determined by its volume and the amount of raw material injected into the mold. In order for the foam to have a uniform surface and a uniform density distribution, the density when foamed in the open state is A foaming agent is added so that the body density is about ½ or less.

Conventionally, chlorofluorocarbon (hereinafter referred to as CFC), especially trichlorofluoromethane (CFC-11), has been mainly used as a foaming agent, but in recent years, CFC destroys the ozone layer in the atmosphere. It is understood that the use and restriction of its use are being promoted. A hydrochlorofluorocarbon (hereinafter referred to as HCF), such as dichlorotrifluoroethane (HCFC-), is used as a freon-based foaming agent having a low possibility of destroying the ozone layer in the atmosphere.
123), chlorodifluoromethane (HCFC-22), or hydrofluorocarbon (hereinafter referred to as HFC), for example, tetrafluoroethane (HFC-134a) as a CFC-based blowing agent that does not destroy the ozone layer.

[0004]

However, HFC-134a, which is a CFC-based blowing agent that does not destroy the ozone layer, has a boiling point of -26.3 ° C., which makes it difficult to handle at room temperature and also causes cost. There are still some supply problems including
From the viewpoints of both cost and environmental problems, it is considered that water foaming, in which water is used for foaming, is advantageous, and this study has been widely conducted (JP-A-5-339338).

By the way, water foaming is mainly used in the production of a low-density soft polyurethane foam of 0.1 g / cm ³ or less (Polyurethane resin handbook / edited by Keiji Iwata / Nikkan Kogyo Shimbun / 178-). (See page 185), when a polyurethane foam having fine cells with a density of 0.2 to 0.8 g / cm ³ is produced by water foaming, a foaming reaction of generating carbon dioxide from water and polyisocyanate and a polyisocyanate It is necessary to surely adjust the balance of the polymerizing reaction in which the polyol reacts, and then, there is a tendency that pinholes are generated on the surface of the foam and the density difference between the parts of the foam becomes large.

When the amount of water is increased in order to improve the surface of the foam, the foaming pressure is increased during foaming, and the foam swells or cracks occur inside after the foam is taken out of the mold. Air voids in the body may cause deformation of the foam surface.

In order to avoid these problems, the time from foaming to demolding must be extended, but for the production of polyurethane foam by the reaction injection molding method, which requires high productivity, this is required. It's a big problem.

As a result of earnest studies to solve the above problems, carbon dioxide adduct of a specific amine compound was used as a foaming agent and a raw material having a low water content was used, so that high productivity and surface condition were obtained. The present invention has been completed by finding that it is possible to produce a polyurethane foam having an excellent low density. A method for producing a polyurethane foam using a carbon dioxide adduct of a specific amine compound as a foaming agent is disclosed in JP-A-7-188367.
In this production method, the amount of the cross-linking agent used is relatively small and a polyurethane foam having sufficient properties cannot be obtained.

[0009]

The present invention is a reaction injection from a mixture of polyisocyanate and a polyol, a catalyst, a blowing agent, a cross-linking agent, and optionally an internal release agent, a reinforcing agent and other auxiliary agents. Depending on the molding method, the density is 0.2-0.8
In the method for producing a polyurethane foam having fine cells of g / cm ³ , a) the blowing agent is a carbon dioxide adduct of an amine compound containing a primary or secondary amino group, and b) a polyol. The water content of the mixture is less than 0.8% by weight, and c) the amount of the crosslinking agent used is 20 per 100 parts by weight of the polyol.
The present invention relates to a method for producing a polyurethane foam, which is characterized in that the amount is from about 1000 parts by weight.

The polyisocyanates used in the present invention include diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, modified polyisocyanates obtained by subjecting these polyisocyanates to urethane modification or carbodiimide modification. Mixtures and the like are available, and diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate, modified polyisocyanates thereof or mixtures thereof are preferable.

The polyol mixture comprises a polyol, a catalyst, a foaming agent, a cross-linking agent, and if necessary, an internal mold release agent, a reinforcing agent and other auxiliaries. As the polyol, propylene glycol, diethylene glycol, glycerin,
Trimethylolpropane, pentaerythritol, sorbitol, sucrose and other hydroxyl group containing compounds, triethanolamine, diethanolamine and other amino group and hydroxyl group containing compounds or ethylenediamine, diaminotoluene and other amino group containing compounds, ethylene oxide, propylene oxide and other A polyether polyol having 2 to 6 hydroxyl groups in the molecule to which an alkylene oxide is added and having an average hydroxyl equivalent of 200 or more, for example, 500 to 3000, or a polymer polyol obtained by addition-polymerizing a vinyl compound to these polyether polyols. Used. Further, a polyester polyol obtained by reacting a polycarboxylic acid and a low molecular weight hydroxyl group-containing compound, a polycarbonate polyol obtained by ring-opening polymerization of caprolactone, an amination of hydroxyl groups of a polyether polyol, or an isocyanate prepolymer of a polyether polyol It may be a polyether polyamine obtained by hydrolyzing a., And having an average active hydrogen equivalent of 200 or more, for example, 500 to 3000. The molecular weight of the polyol is 1000 or more, preferably 100.
It may be 0 to 18000, for example 2000 to 8000. The amount of polyol may be 5 to 80 parts by weight, for example 15 to 50 parts by weight, per 100 parts by weight of the polyol mixture.

As the catalyst, triethylenediamine, pentamethyldiethylenetriamine, 1,8-diazabicyclo-5,4,0-undecene-7, dimethylaminoethanol, tetramethylethylenediamine, dimethylbenzylamine, tetramethylhexamethylenediamine, bis ( Tertiary amines such as 2-dimethylaminoethyl) ether and organometallic compounds such as dibutyltin dilaurate, tin octoate and dibutyltin diacetate are used.
The amount of catalyst is 0.1 per 100 parts by weight of the polyol mixture.
It may be from 1 to 5 parts by weight.

The blowing agent is an amine compound containing a primary or secondary amino group, such as ethylenediamine,
Hexamethylenediamine, polyamines such as diethylenetriamine and triethylenetetramine, alkanolamines such as ethanolamine, N-methylethanolamine, diethanolamine, isopropanolamine and diisopropanolamine, preferably carbon dioxide adducts of alkanolamines, which are amines. When the compound is heated to 30 to 110 ° C., preferably 50 to 80 ° C., and carbon dioxide of 1 to 5 Bar is blown in while slowly stirring, the compound can be easily synthesized in a relatively short time. Usually, the reaction ends at the stage when 1 mol of carbon dioxide is absorbed in 2 amine equivalents of the amine compound, and the heat generation stops. Since this reaction liquid tends to solidify at room temperature, it is preferable to add to the amine compound half or more of the liquid polyol or crosslinking agent in advance. A low boiling point hydrocarbon, a freon-based foaming agent, nitrogen gas, air or the like may be partially used as a foaming agent. The amount of the foaming agent used is 1 to 30 parts by weight per 100 parts by weight of the polyol mixture,
For example, it may be 2 to 10 parts by weight.

However, the combined use of water as a foaming agent is not very preferable. As the degree of water foaming relative to amine compound foaming increases, the foaming pressure increases, which adversely affects demolding in a short time. However, mixing of water is unavoidable from the viewpoint of handling the raw material such as addition of a reinforcing agent, but the amount must be 0.8% by weight or less, preferably 0.5% by weight or less of the polyol mixture. 0.8% by weight
If more, the foam will swell when removed from the mold in a short time,
Cracks may occur, and the productivity of the polyurethane foam may be reduced accordingly.

The cross-linking agent has a molecular weight of 62 to 1,000.
Polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol,
Neopentyl glycol, glycerin, trimethylolpropane, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol and polyvalent amines such as diethyltoluenediamine, t-butyltoluenediamine, diethyldiaminobenzene, triethyldiaminobenzene, tetraethyl. Diaminodiphenylmethane and the like are used as needed, and polyether polyols and the like in which alkylene oxide is added are also used. JP-B-54-17359, JP-B-1-34527, and JP-A-57-74325. , JP-B-63-47
No. 726, etc. The molecular weight of the cross-linking agent is less than 1000 (62-1000), for example 62-
It may be 500. The amount of the cross-linking agent used is polyol 1
It is 20 to 1000 parts by weight, but may be 20 to 300 parts by weight, for example, per 00 parts by weight.

As the internal mold release agent, a mixture of a carboxylic acid metal salt and an amine (Japanese Patent Publication No. 63-52056) and a reaction product of polysiloxane and isocyanate (Japanese Patent Publication No. 58-1).
139), a mixture of amine, aliphatic carboxylic acid salt and carboxylic acid ester (Japanese Patent Publication No. 55-42091), hydrogenated castor oil (Japanese Patent Publication No. 4-20925), ester of fatty acid polyester and lower alkyl acetoacetate. Exchange products (Japanese Patent Laid-Open No. 5-155969) and the like are used as necessary.

The reinforcing agent is a fiber such as glassy material, inorganic material, or mineral material, for example, milled glass fiber, wollastonite fiber, processed mineral fiber or flake, for example, mica, glass flake, etc., and is used as necessary. . It is also possible to set a glass mat, a glass cloth, etc. in advance in a mold and then inject a polyurethane raw material thereover to obtain a foam.

Other auxiliary agents include foam stabilizers such as silicone type foam stabilizers, surfactants, weathering agents such as antioxidants, UV absorbers and stabilizers such as 2,6-di-t-butyl-. 4-methylphenol, tetrakis [methylene
3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, a colorant and the like are used as necessary.

For the production of polyurethane foam by the reaction injection molding method, polyurethane engineering RR
A reaction injection molding machine such as a high-pressure polyurethane foaming machine for IM is used.

When a mixture of polyisocyanate and polyol is injected into a mold by a reaction injection molding method using a high-pressure polyurethane foaming machine or the like, the raw material is expanded and expanded in the mold and then cured, so that the polyurethane foam can be taken out. it can.

[0021]

[Function] The amine compound, which is a foaming agent, reacts with polyisocyanate to release carbon dioxide, and the remaining amine reacts with polyisocyanate to form a urea bond. Since it flows through the inside, the inside of the mold can be filled with a lower density, and a foam having a predetermined density can be obtained with a smaller amount of generated gas with a low overback ratio. Further, the foaming pressure of the raw material at the time of demolding is reduced, and even if the material is demolded in a short time, it does not crack or swell, the density distribution is uniform, and pinholes and voids are less likely to occur on the foam surface. .

[0022]

EXAMPLES A synthetic example of an amine compound used in the present invention will be shown in Reference Examples, and the present invention will be specifically described with reference to Examples and Comparative Examples. Parts are parts by weight.

Reference Example 1 A 10-liter double-jacket pressure-resistant reaction vessel having a rotor of 60 rpm, 2.39 kg of ethanolamine, N-
2.94 kg of methyl ethanolamine and 2.94 kg of ethylene glycol were added and the mixture was heated to 50 ° C. with stirring. A carbon dioxide bomb equipped with a pressure reducing valve was connected to this container, and carbon dioxide depressurized to 3 atm was supplied to the liquid portion while stirring. The liquid temperature rose to 90 ° C. in about 3 hours and then slowly dropped back to 50 ° C. The liquid was withdrawn from the container 8 hours after supplying carbon dioxide and weighed 9.95 kg. This liquid was stable even at room temperature, and no abnormal generation of gas was observed even when heated to 80 ° C., and could be stored in a 20 liter tin can as it was. This liquid 280
When g was put in a pressure-resistant container with a pressure gauge of 300 cc and heated at 50 ° C. in a sealed state, the pressure became 0.17 Bar. When the pressure generated by air expansion was subtracted, the vapor of this liquid was only 0.07 Bar.

Reference Example 2 In the same pressure resistant reactor as in Reference Example 1, ethanolamine 1.
04 kg, N-methylethanolamine 2.57 kg, diethanolamine 1.8 kg and ethylene glycol 3.0
8 kg was added and the mixture was heated to 50 ° C. with stirring. A carbon dioxide bomb equipped with a pressure reducing valve was connected to this container, and carbon dioxide depressurized to 1 atm was supplied to the upper portion of the liquid while stirring. The liquid temperature rose to 90 ° C. in about 7 hours, then slowly dropped and returned to 50 ° C. The liquid was withdrawn from the container 12 hours after the carbon dioxide was supplied and weighed to be 9.97 kg.
This liquid was stable at room temperature, and no abnormal gas generation was observed even when heated to 80 ° C., and it was possible to store it in a 20-liter tin can as it was. When 100 g of this liquid was placed in a beaker and 70 g of phosphoric acid was slowly added dropwise, gas was violently generated. After the gas generation was completed, the weight was measured and found to be 155.2 g.

Reference Example 3 In the same pressure resistant reaction vessel as in Reference Example 1, ethanolamine 3.
67 kg and 4.99 g of ethylene glycol were added,
Warm to 50 ° C. with stirring. A carbon dioxide bomb equipped with a pressure reducing valve was connected to this container, the pressure was reduced to 3 atm, and carbon dioxide was supplied to the upper portion of the liquid while stirring. The liquid temperature rose to 100 ° C. in about 30 minutes and then slowly dropped back to 50 ° C. The liquid was withdrawn from the container 4 hours after supplying carbon dioxide and weighed 9.98 kg. This liquid was at room temperature.

Example 1 Polyether polyol having an OH number of 880 mgKOH / g obtained by adding propylene oxide to trimethylolpropane.
(Crosslinking agent) 60 parts, 40 parts of polyether polyol (polyol) having an OH value of 35 mgKOH / g, which is obtained by adding propylene oxide and ethylene oxide to glycerin, and 33% dipropylene glycol solution of triethylenediamine (catalyst).
1.5 parts of a 70% solution of bis (2-dimethylaminoethyl) ether in dipropylene glycol (manufactured by Tosoh: Toyocat
1 part (ET, catalyst), 0.5 part of water and 9 parts of the amine compound obtained in Reference Example 1 were mixed well, and milled glass fiber (manufactured by Nitto Boseki: SS-10-404, reinforcing agent) 51.
6 parts were added and stirred. 30 kg each of this polyol mixture and polymethylene polyphenyl isocyanate having an isocyanate group content of 31.5% containing 40% of polynuclear body were prepared respectively, and were prepared by using a high pressure polyurethane foaming machine for R-RIM (Polyurethane Engineering Co .: MC-106). After putting in the tank and adjusting the liquid temperature to 40 ℃, mix ratio 100: 113
(Weight ratio), discharge rate 450g / sec, mixing pressure 160kg / c
m ² with injection time of 1 second, its size is 900mm × 300mm
It was poured into a 4 mm sheet metal mold from one short side, and the pressure inside the mold was measured by a pressure sensor placed 7.5 cm from the injection part. The maximum mold pressure was 2.3 kg / cm ² .

45 seconds after the injection, the foam was taken out of the mold,
After standing for 48 hours at 25 ° C. and 50% humidity, the density distribution and physical properties were measured, and both showed the same results as in the case of water foaming. Table 2 shows each measured value. Also, molds of the same size with partial thicknesses of 10 mm, 15 mm, 20 mm,
Similarly, after 45 seconds, the foam was taken out from the mold using a mold designed to have a thickness of 25 mm and surface defects due to internal cracks were observed in each thick part. There were no major defects. The results are shown in Tables 1 and 2.

Example 2 The same amount of the same polyol, crosslinking agent and catalyst as in Example 1 was used except that the amine compound obtained in Reference Example 3 was used, and milled glass fiber (SS-10-40 manufactured by Nitto Boseki Co., Ltd.) was used.
4) Using the polyol mixture obtained by adding and stirring 52.4 parts, a foamed product was obtained under the same conditions as in Example 1 except for the mixing ratio of 100: 115 (weight ratio), and good results were obtained as in Example 1. . The results are shown in Tables 1 and 2.

Comparative Example 1 The amine compound obtained in Reference Example 1 was removed from the raw material used in Example 1, and water was added to 1.2 parts instead of this, and milled glass fiber (SS-10 manufactured by Nitto Boseki Co., Ltd.) was added. -404) 4
Using a polyol mixture (moisture content measured value 0.9%) to which 6.7 parts was added and stirred, the raw materials were injected into the mold under the same conditions as in Example 1 except that the mixing ratio was 100: 110 (weight ratio). The maximum pressure inside the mold was as high as 4.5 kg / cm ^2, and due to this, surface defects due to internal cracks were observed in all the thick parts except the thick part of 4 mm. The results are shown in Tables 1 and 2.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

EFFECTS OF THE INVENTION According to the present invention, a raw material foamed with an amine compound exhibits extremely excellent flowability, can be easily filled in a mold, and can be demolded in a shorter time than water foaming. Even if it does not swell at all, a low density polyurethane foam having excellent surface properties can be produced.

Claims (2)

[Claims] 1. A mixture of polyisocyanate, a polyol, a catalyst, a foaming agent, a cross-linking agent and, if necessary, an internal mold release agent, a reinforcing agent and other auxiliaries and having a density of 0. A method for producing a polyurethane foam having minute cells of 2 to 0.8 g / cm ³ , wherein a) the foaming agent is a carbon dioxide adduct of an amine compound containing a primary or secondary amino group. B) the water content of the polyol mixture is less than or equal to 0.8% by weight, and c) the amount of crosslinking agent used is 20 per 100 parts by weight of polyol.
~ 1000 parts by weight, a method for producing a polyurethane foam. 2. The method for producing a polyurethane according to claim 1, wherein the polyisocyanate is polymethylene polyphenyl isocyanate and the blowing agent is a carbon dioxide adduct of alkanolamine.