JPH05306318A - Production of polyurethane foam having high-density skin layer - Google Patents

Abstract

PURPOSE:To produce a product in a short demolding time in high productivity without using a halogenated hydrocarbon foaming agent to cause the deterioration of environment by using water as the exclusive foaming agent and a specific amine compound as a catalyst. CONSTITUTION:This product is produced by reacting a polyol with a polyurethane in the presence of a foaming agent composed exclusively of water, a catalyst composed of an amine compound of formula (R1 to R4 are 1-12C alkyl or together with adjacent N form cycloalkyl ring, etc.; R5 is H, phenyl, etc.) and, as necessary, other assistant. The amine compound of formula is preferably N,N',N'-tetramethylguanidine and the use of the compound in the form of a salt of a higher fatty acid such as 2-ethylhexanoic acid is further preferable in view of the catalytic activity. The polyisocyanate is preferably diphenylmethane-4,4'-diisocyanate, etc., having high reactivity to shorten the demolding time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyurethane foam having a high density surface layer such as soft, semi-hard or hard. More specifically, it relates to a method for producing a polyurethane foam having a high-density surface layer using water without using halogenated hydrocarbons as a blowing agent, that is, a so-called integral skin foam.

[0002]

BACKGROUND OF THE INVENTION Polyurethane foam is usually foamed by instantly stirring and mixing a polyisocyanate with a polyol premix containing a polyol, a catalyst, a blowing agent (halogenated hydrocarbon and / or water), and optionally other auxiliary agents. Is manufactured.

Integral skin foam is used in various products because of its light weight, soft feeling and excellent impact resistance. For example, it has been used for a handle, an air spoiler, a bumper, a headrest, an armrest, a structural foam and the like as an interior / exterior material for an automobile.

These products are produced by a conventionally known method, for example, the method described in pages 220 to 221 of Polyurethane Resin Handbook (edited by Keiji Iwata) and Polyurethane.
eHand Book (Gunter Oertel
Pp. 314-369. According to these known methods, the integral skin foam is an integrally molded product with a high-density surface layer portion (skin) and a low-density central portion (core) simultaneously with a single injection and foaming operation using the same system liquid. Moreover, it is obtained with high productivity.

This advantage is due to a manufacturing technique, that is, CFC-11 (trichloromonofluorocarbon) as a foaming agent.
It is achieved by increasing the overpack ratio of a highly reactive polyol system, which requires the use of the above, and performing foam molding by the RIM method (reaction injection molding). As a catalyst, triethylenediamine and tin compounds are generally used and have been easily produced. The principle that the surface layer of integral skin foam has high density is CFC-1 which is a CFC-based foaming agent.
CFC-11 due to physical condensation (pressure increase due to high overpack ratio and low temperature due to absorption of reaction heat into the mold) in the surface layer portion of the mold 1.
This is the reason why the use of is mandatory.

However, CFC-11, which is a halogenated hydrocarbon blowing agent at present, has been completely abolished in this century as one of the causative substances causing the destruction of the ozone layer of the earth. Therefore, there is a demand for a system and manufacturing technique for manufacturing integral skin foam that does not use CFC-11 as a foaming agent. As an improved technique for these, a low boiling point solvent such as pentane or HCFC-
123, HCFC-22, HCFC-141b, and other so-called CFC substitutes having a small ozone depletion coefficient have been proposed. However, the low boiling point solvent has a problem of flammability, but the alternative CFC does not have an ozone depletion potential of zero and cannot be used in the future, and neither is a fundamentally sufficient solution technology. Further, as a pollution-free type, there is a so-called gas loading method using dry air or nitrogen gas, but the above-mentioned physical condensation is impossible and it is difficult to form a high-density surface layer. On the other hand, the method of using water (reacting with isocyanate and generating CO ₂ gas) conventionally used for polyurethane foam as a foaming agent has high safety and does not have the above environmental problem, but compared with CFC-11 foaming. It is difficult to obtain a high-density surface layer. As an improved technique, a method using a special catalyst (Japanese Patent Laid-Open No. 3-32811 and Japanese Patent Laid-Open No. 3-33120).
Is being considered. However, although a relatively high-density surface layer portion can be obtained, it is not satisfactory, and there is a problem that the demolding time from the mold is long and the productivity is low.

That is, a technique for producing a polyurethane foam product having a high-density surface layer with high productivity and without deteriorating the environment is strongly desired.

[0008]

In view of the above circumstances, the present invention provides a method for producing an integral skin foam using only water without using halogenated hydrocarbons as a blowing agent with high productivity. It is a thing.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies on a method for producing an integral skin foam using water as a foaming agent.

As a result, a new fact was found that the surface layer of a foam can be densified and the demolding time can be shortened by using a guanidine amine compound and / or its organic acid salt as a catalyst. Has been completed.

That is, the present invention is a method for producing a polyurethane foam by reacting a polyol and a polyisocyanate in the presence of a foaming agent, a catalyst and, if necessary, other auxiliary agents. The present invention also provides a method for producing a polyurethane foam having a high-density surface layer, characterized by using an amine compound represented by the following general formula (I) and / or an organic acid salt thereof as the catalyst. ..

[0012]

[Chemical 2]

(In the formula, R _{1 to} R _{4 each} independently represent a C _{1 to} C ₁₂ alkyl group or may form a cycloalkyl ring or a heterocycle with an adjacent nitrogen. R ₅ is hydrogen or C ₁
Alkyl group, a phenyl group -C _12, a cycloalkyl group) The present invention will now be described in more detail. The present invention is
It is a method for producing a molded product obtained by injecting and foaming a mixed solution of a polyol premix containing a polyol, a catalyst, water and, if necessary, other auxiliary agents and polyisocyanate, which is stirred, into a mold.

The catalyst used in the production method of the present invention is a guanidine amine compound represented by the general formula (I) and / or an organic acid salt thereof.

As the guanidine-based amine compound,
N, N, N ', N'-tetramethylguanidine, N,
N, N ', N', N "-pentamethylguanidine, N,
N, N ', N'-tetramethyl-N "-cyclohexylguanidine, N, N, -diethyl-N', N'-dimethylguanidine, N, N, -diethyl-N ', N'-dimethyl-N" -Methylguanidine, N, N, -diethyl-
N ', N'-dimethyl-N "-cyclohexylguanidine and the like can be exemplified, but N, N, N', N'-tetramethylguanidine is more preferable. However, these guanidine-based amine compounds are gradually added in the presence of water. When the water is used as the blowing agent as in the production method of the present invention, the catalyst functions only for a short period of time after mixing with the polyol premix, which is disadvantageous. Can be solved by using a guanidine-based amine compound in the form of a salt with an organic acid, such as an aliphatic saturated carboxylic acid or an aliphatic unsaturated carboxylic acid having an acid dissociation index pKa in the range of 3 to 6. Acids, aromatic carboxylic acids, amino acids, etc., such as formic acid, acetic acid, 2-
Ethyl hexanoic acid, oleic acid, acrylic acid, crotonic acid, citric acid, adipic acid, succinic acid, benzoic acid, 4-
Examples thereof include aminobutyric acid, but salts with higher fatty acids such as 2-ethylhexanoic acid and oleic acid are more preferable because of high catalytic activity. A weak acid with an acid dissociation index pKa higher than 6,
For example, with carbonic acid and phenol, hydrolysis still proceeds and the catalytic activity gradually decreases. On the other hand, a strong acid having an acid dissociation index pKa of less than 3, such as hydrochloric acid or dichloroacetic acid, does not hydrolyze, but the salt itself has a low catalytic activity and does not function as a catalyst.

The amount of the catalyst used in the production method of the present invention is usually 0.0 when the polyol is 100 parts by weight.
2 to 10 parts by weight. If the amount used is large, the reactivity of the system becomes high and the demolding time can be shortened, but the economical efficiency is reduced. On the contrary, when the amount used is small, the demolding time becomes somewhat long. A more preferable range of the amount of catalyst used is 0.
5 to 5.0 parts by weight. Known tertiary amine catalysts and / or organic carboxylates or organometallic compounds thereof, which are usually used as cocatalysts, can be appropriately used as co-catalysts as long as the function of the catalyst of the present invention is not lost. Of these cocatalysts, the amine catalysts include triethylenediamine, 1-
Methyl-4- (2-dimethylaminoethyl) piperazine, 1-methyl-4- (2-hydroxyethyl) piperazine, bis (2-dimethylaminoethyl) ether, tetramethylhexamethylenediamine, 1-methylimidazole, 1, 2-Dimethylimidazole, 1-isobutyl-2-methylimidazole, tris (dimethylaminopropyl) hexahydro-S-triazine or organic acid salts thereof are preferable, and they improve moldability in the production method of the present invention. Examples of the organometallic compound are organotin compounds and alkali metal salts of carboxylic acids, such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin bis (isooctyl mercaptoacetate), potassium acetate, 2-ethylhexanoic acid. Potassium and the like are preferable, and in the production method of the present invention, the organotin compound particularly shortens the demolding time.
These catalysts and the guanidine-based amine compound of the present invention and / or the organic acid salt catalyst thereof can be used in any combination, but the guanidine-based amine compound and / or the organic acid salt thereof and the amine catalyst as a cocatalyst are used. A combination, and further, a combination of three kinds with an organotin compound are more preferable, and a foam having a higher density surface layer can be produced with good moldability in a short time. The use ratio of the three combinations is in the range of 0.1 to 5 parts by weight of an amine catalyst as a cocatalyst and 0 to 0.5 parts by weight of an organotin compound with respect to 1 part by weight of a guanidine amine compound and its organic acid salt. Used in.

As the foaming agent used in the production method of the present invention, only water which reacts with isocyanate to generate carbon dioxide gas is used. The amount of water used is determined according to the density of the desired product. A large amount of low density product and a small amount of high density product can be obtained.
Usually 5 parts by weight or less is used.

The polyisocyanate used in the production method of the present invention is a known aromatic polyisocyanate, for example, toluene diisocyanate, diphenylmethane-4,
4'-diisocyanates, their polymerized isocyanates, or toluene diisocyanate prepolymers obtained by reacting them with polyols, diphenylmethane-4,
Examples thereof include isocyanate-terminated prepolymers such as 4′-diisocyanate prepolymers; modified isocyanates such as carbodiimide-modified; and mixed polyisocyanates thereof. Preferably, highly reactive diphenylmethane-4,4'-diisocyanate, polymer isocyanate thereof and isocyanate-terminated prepolymers thereof, modified isocyanate and mixed polyisocyanate thereof are suitable for shortening demolding time. It should be noted that the aliphatic and alicyclic isocyanates have somewhat low reactivity and the demolding time becomes somewhat longer.

In the production method of the present invention, a conventionally known polyol, a cross-linking agent and, if necessary, a foam stabilizer and other auxiliaries can be used.

Examples of the polyol include polyether polyol, polymer polyol and polyester polyol having two or more reactive hydroxyl groups. Examples of the polyether polyol include glycol, glycerin,
Pentaerythritol, polyhydric alcohols such as sucrose, ammonia, aliphatic amine compounds such as ethyleneamine, toluenediamine, diphenylmethane-4,
An aromatic amine compound such as 4′-diamine and / or a polyether polyol obtained by adding ethylene oxide or propylene oxide to a mixture thereof may be used. Examples of the polymer polyol include those obtained by reacting the polyether polyol with an ethylenically unsaturated monomer such as butadiene, acrylonitrile and styrene in the presence of a radical polymerization catalyst. Examples of the polyester polyol include those produced from a dibasic acid and a polyhydric alcohol, such as polyethylene adipate and polyethylene terephthalate type, and these may be those regenerated from wastes. Of these, a bifunctional or trifunctional polyol is used for a relatively elastic flexible foam, a semi-rigid foam, or the like, and a trifunctional or higher functional polyol is preferably used for a relatively inelastic rigid foam.

The cross-linking agent is a known bifunctional or higher functional low molecular weight polyol, such as ethylene glycol, diethylene glycol, butanediol, trimethylolpropane, glycerin or other low molecular weight polyols, triethanolamine, diethanolamine or other low molecular weight amines. Examples thereof include polyol. These low molecular weight polyols are used alone or in combination of two or more.

As the foam stabilizer, for example, organopolysiloxane-polyoxyalkylene copolymer, silicone-
It is a nonionic surfactant such as a glycol copolymer, or a mixture thereof, and is used as necessary.
Although the amount thereof is not particularly specified, it is usually 0 to 2.5 parts by weight with respect to 100 parts by weight of the polyol.

In the present invention, if necessary, other auxiliary agents can be added, and examples include conventionally known flame retardants, colorants, extenders, antioxidants, and UV inhibitors. The mixing ratio of the polyol premix and the polyisocyanate, the so-called index, is 60 to 150, preferably 80 to 120. The mixed liquid thus obtained is mixed by a foaming machine, and is poured and foamed into a mold to be a product after demolding. As the foaming machine, either high pressure or low pressure can be used, but a high pressure machine with good mixing is preferable. Further, the injection amount of the mixed liquid is an amount that causes an overfilling state in the mold, which is a so-called overpacking state. The higher the overpacking rate, the higher the density of the surface layer portion obtained, but it goes without saying that there is a limit.

As the mold, an open mold, a closed mold, RIM and the like can be used, but RIM molding is preferable because it can shorten the demolding time. Further, the lower the mold temperature is, the higher the density of the surface layer portion is obtained, but the resin is insufficiently formed and the demolding time becomes long. Therefore, the range of 30 to 60 ° C. is preferable.

The products obtained by the manufacturing method of the present invention include, for example, handles as interior and exterior materials for automobiles, instrument panels, headrests, armrests, door panels, air spoilers, bumpers, and structural foams as other structural materials. Is mentioned.

[0026]

INDUSTRIAL APPLICABILITY The production method of the present invention is a completely new and effective production method which does not damage the global environment while maintaining the product properties and productivity of the conventional production method using halogenated hydrocarbons. Is.

[0027]

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to these examples.

Examples 1 to 6 and Comparative Examples 1 to 5 In the formulations having the following mixing ratios (formulations) of the raw materials, the catalysts of the Examples and Comparative Examples were used, and predetermined foaming conditions were used. A lower foaming test was performed. Of these, in Example 1, the amount of water was 0.8 parts by weight to produce a foam having a relatively low density. In Example 2, the amount of water was 0.5 part by weight, and a larger amount of the mixed liquid was poured into the mold to cause foaming to produce a higher density foam. In the third embodiment, the mold temperature is higher than that of the first embodiment by 10 ° C. 50
℃ was made. In Examples 4 to 6 and Comparative Examples 1 to 5, the foaming test was performed under the same conditions as in Example 1 except for the catalyst. The amount of catalyst used in each example has the same reactivity (rise time of about 60 seconds)
And the amount. The generated foam was evaluated by the following method. The results are shown in Table 1.

[0029] 1) Trifunctional polyether polyol, OHV = 33m
gKOH / g (manufactured by Sanyo Kasei Co., Ltd., FA-703) 2) Ethylene glycol (manufactured by Nisso Yuka Co., Ltd.) 3) Description of catalyst used and catalyst abbreviation in table TMG; N, N, N ′, N′-Tetramethylguanidine PMG; N, N, N ′, N ′, N ″ -Pentamethylguanidine CHMG; N, N, N ′, N′-Tetramethyl-N ″ -cyclohexylguanidine L33E; Triethylenediamine 3
3 wt% ethylene glycol solution (manufactured by Tosoh Corporation,
TEDA-L33E) POLYCAT-41; tris (dimethylaminopropyl) hexahydro-S-triazine (manufactured by Air Products) POLYCAT-42; mixture of tris (dimethylaminopropyl) hexahydro-S-triazine and organic metal salt ( Air Products Co., Ltd.) NMIZ; N-methylimidazole DBU; 1,8-diazabicyclo (5,4,0) undecene-7 phenol salt (San Apro Co., Ltd., UC)
ATSA1) 4) Crude MDI, NCO concentration = 31.0% (manufactured by Nippon Polyurethane Industry Co., Ltd., MR-200) b. Foaming conditions Raw material liquid temperature 25 ± 1 ° C. Stirring speed 6000 rpm (6 seconds) c. Measurement items Free foaming / reactivity At room temperature (20-25 ° C), the mixed solution is poured into a 500 ml polyethylene cup to foam, and the reactivity is measured.

Cream time; foam rise time (seconds) Gel time; resin (stringing) time (seconds) Rise time; foam rise stop time (seconds) Aluminum with internal dimensions of 15 × 20 × 1 cm adjusted for mold foaming temperature After injecting the mixed solution into the mold, the upper lid was quickly closed to cause foaming. After 4 minutes, the molded foam was demolded and evaluated for the following items: Demoldability 4 minutes demolding foam hardness (Shore C) was measured and compared. ・ Final hardness Foam hardness 1 day after foaming (Shore C) The foam density was calculated from the size and weight of the foam sampled from three points in the center of the foam, and the average value was taken as the overall density. The surface layers (upper and lower) of the sampled foam were cut by 2.5 mm to calculate the density, and the average value was used as the surface layer density. The central part density was calculated from the remaining central part foam cut for calculating the surface layer part density. The difference between the surface layer density and the center density was compared and evaluated. That is, it can be said that a foam having a higher density surface layer has a larger difference.

[0031]

[Table 1]

As is clear from Table 1, the foam produced by using the catalyst of the present invention has high demolding hardness and excellent demolding property, and the surface layer has a higher density. On the other hand, the foam produced using the catalyst of Comparative Example has low demolding hardness and low surface layer density.

Examples 7 to 10 and Comparative Examples 6 to 9 A storage stability test at the time of polyol premixing was conducted on the catalyst prepared by reacting 1 mol of various acids with 1 mol of TMG (tetramethylguanidine) and TMG itself. did. The abbreviation and composition of the catalyst reacted with the acid and the method for the storage stability test are shown below. The results are shown in Table 2.

Preparation of TMG Acid Salt Catalyst A 300 ml round bottom flask was charged with a predetermined amount of TMG and ethylene glycol (EG) or water as a solvent, and an acid was added with stirring. The composition of each produced catalyst is shown below (all numerical values represent% by weight).

TMG-FA; TMG40.0, formic acid (9
5%) 17.0, EG43.0 TMG-AA; TMG40.0, acetic acid 20.9, EG3.
9.1 TMG-HA; TMG30.0, 2-ethylhexanoic acid 37.6, EG32.4 TMG-P; TMG35.0, phenol 28.6, E
G36.4 TMG-C; TMG40.0, carbon dioxide 15.3, E
G34.7, water 10.0 TMG-DA; TMG30.0, dichloroacetic acid 33.
6, EG36.4 TMG-CA; TMG30.0, hydrochloric acid 9.5, EG4
3.6, water 16.9 Method of storage stability test Same formulation as in Example 1 (Polyol 1
(00 parts by weight, 0.8 parts by weight of water, 8 parts by weight of ethylene glycol) were added and premixed with TMG and the acid salt catalyst of TMG shown in Table 2. Immediately after the premix and 5
After storage in an oven at 0 ° C. for 6 days, a foaming test was performed to measure the reactivity and compare the activity and stability of the catalyst.

[0036]

[Table 2]

As is clear from Table 2, TMG has a slow reactivity after being stored for 6 days and thus has poor stability. TMG formate, acetate and 2-ethylhexanoate have almost the same reactivity and good stability. A salt of carbonic acid or phenol and TMG having an acid dissociation index pKa higher than 6 has poor reactivity because of slow reactivity. On the other hand, a salt of hydrochloric acid or dichloroacetic acid with TMG having an acid dissociation index pKa of less than 3 has low catalytic activity and does not function as a catalyst.

Examples 11-18, Comparative Examples 10-12 In the same formulation as in Example 2, the TM
A foaming test was conducted on G-HA, TMG-FA, and a combination system of these with an amine catalyst as a cocatalyst and an organotin compound. The reactivity was enhanced by using a large amount of the catalyst, and the demolding time was evaluated at 2 minutes. At the same time, the formability of the foams obtained was evaluated. The evaluation criteria are shown below. The results are shown in Table 3. Further, the abbreviated catalyst names and chemical names in the tables of the amine catalysts and organotin compounds used are shown below.

Evaluation of moldability ⊚: No void ∘: Some voids △: Some voids ×: Many voids Explanation of catalyst abbreviation in the table TMNAEP; 1-methyl-4- (2-dimethylaminoethyl) ) Piperazine (Tosoh Corp., TOYOCAT)
-NP) MHEP; 1-methyl-4- (2-hydroxyethyl) piperazine (Tosoh Corp., TOYOCAT-H
P) BDAEE; bis (2-dimethylaminoethyl) ether 70 wt% dipropylene glycol solution (TOSOCAT-ET, TOYOCAT-ET) DBTDL; dibutyltin dilaurate (TOSO-TEDA, TEDA-T411) DBTM; dibutyl Chin bis (isooctyl mercaptoacetate) (manufactured by Tosoh Corporation, TEDA-T40)
S)

[0040]

[Table 3]

As is apparent from Table 3, the foam produced by using the catalyst of the present invention has high demolding hardness, excellent demolding property, and good moldability, and the surface layer has a higher density. There is.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C08G 101: 00) C08L 75:04

Claims (3)

[Claims] 1. A method for producing a polyurethane foam by reacting a polyol and a polyisocyanate in the presence of a foaming agent, a catalyst and, if necessary, other auxiliary agents, using only water as a foaming agent, and further adding a catalyst. A method for producing a polyurethane foam having a high-density surface layer, characterized in that an amine compound represented by the following general formula (I) is used as [Chemical 1] (In the formula, R _{1 to} R ₄ represent an independent C _{1 to} C ₁₂ alkyl group, or a cycloalkyl ring together with an adjacent nitrogen,
A heterocycle may be formed. R ₅ represents hydrogen, a C ₁ -C ₁₂ alkyl group, a phenyl group or a cycloalkyl group) 2. The method according to claim 1, wherein the polyisocyanate is an aromatic isocyanate having two or more isocyanate groups. 3. The catalyst according to claim 1, wherein the catalyst is an addition salt of an amine compound represented by the general formula (I) and an organic acid having an acid dissociation index pKa in the range of 3 to 6. Two
The manufacturing method described in.