JPH0762053A - High-density internal skin form - Google Patents

Abstract

PURPOSE:To obtain a polyurethane foam having integral skin by using a specific polyol component and using water as exclusive foaming agent without using fluorocarbon foaming agent. CONSTITUTION:This integral skin foam having an integral skin layer of 0.5-0.8mm thick can be produced by the reaction injection molding of a polyisocyanate component and a polyol component produced by adding 7.5 pts.wt. of a crosslinking agent, 2.04 pts.wt. of a catalyst, 0.45 pts.wt. of water as a foaming agent and 1 pt.wt. of a pigment to a polyol composed of 70 pts.wt. of a trifunctional polyether polyol having a molecular weight of 6,000 and 22.5 pts.wt. of a specific bifunctional polyether polyol containing 31wt.% of ethylene oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane foam having a relatively high density and an integral skin layer (hereinafter referred to as an integral skin foam). The integral skin foam of the present invention is used for steering wheels, airbag covers (module covers, horn pad covers), armrests, shift knobs and the like.

[0002]

2. Description of the Related Art As a typical application of integral skin foam, for example, a steering wheel is formed by coating a core material such as steel with a polyurethane foam having an integral and dense surface layer. JP-A-3-32811 and JP-A-3-33120
JP, JP-A-2-296815, JP, 3-2
No. 20223, No. 4-132719, No. 4-85342, No. 2-199136, No. 4-180912, No. 3-24
108, JP-A-4-226313, JP-A-4-152116, JP-A-4-325533, etc.). The product in which the skin layer and the foam layer are integrally molded as in the above-described molded product has excellent tactile sensation, and not only the steering wheel but also many products such as an airbag cover and an armrest are similarly molded.

As a foaming agent for forming the integral skin, a fluorocarbon type foaming agent which is a low boiling point organic compound has been generally used, and in particular, chlorofluorocarbons represented by trichlorofluoromethane (CFC 11). Is often used. However, the use of fluorocarbons, especially chlorofluorocarbons, has become a global environmental problem because it destroys the ozone layer, and their use is regulated or restricted internationally, and this type of blowing agent is becoming unusable. .

Therefore, the use of CFC22, CFC123, CFC141b, etc. as a substitute foaming agent for CFC11 has been studied, but these fluorohydrocarbon type foaming agents are not completely free from the problem of ozone layer depletion. It is becoming more and more subject to regulation, and there is a high possibility that it will become unusable in the future. Further, all of the above alternative foaming agents have a low boiling point or have a high solubility in resin, and therefore, simply replacing CFC 11 in the conventional integral skin foam formulation causes large shrinkage of the demolded foam. There is also a problem that it may cause collapse or collapse. In addition, the use of organic solvents such as methylene chloride and 1,1,1-trichloroethane as alternative foaming agents is also being considered, but these organic solvents dissolve in the foam produced and the product after demolding Has a problem of becoming soft or shrinking beyond the limit.

Since the physical foaming agent has various problems as described above, the use of a chemical foaming agent (a foaming agent which generates a gas by a reaction) is also being studied. In particular, in the case of urethane foam, carbon dioxide is produced by the reaction between isocyanate and water, and therefore various uses of water as a foaming agent have been studied. However, the use of water alone as the foaming agent generally causes the following problems. Decrease in molding shrinkage: When CFC 11 is used, the product after mold release shrinks to some extent, but when water is used,
The product rather expands. Therefore, when the conventional mold designed in consideration of shrinkage of the product is used as it is, the product is finished to have a size larger than a predetermined size.

Decrease in fluidity of raw material in mold: Freon 11 has extremely low viscosity, and the conventional polyol component blended with it has relatively low viscosity. Therefore, the raw material injected into the mold also has excellent fluidity according to each step of the reaction.
However, when water is used as a foaming agent, the viscosity of the raw material increases and the fluidity decreases. Deterioration of skin layer forming ability: Water is also a kind of chemical foaming agent, and as a matter of course, the entire foam is uniformly foamed, which makes it difficult to form a skin layer. Occurrence of stirring failure in high pressure stirring method: Integral skin foam is generally molded by reaction injection molding (RIM). In RIM, stirring is performed by collision-mixing the two components at high pressure. However, as described above, when water is used, the viscosity of the polyol component increases, and the viscosity of the isocyanate component does not change significantly. The balance of the viscosities of the two components colliding with each other is lost, resulting in poor stirring.

[0007]

The present invention uses only the above-mentioned water as a foaming agent by not using a CFC-based foaming agent which has a problem of ozone layer depletion and by using a specific polyol component. It is an object to solve various problems in the case and provide an integral skin foam having excellent properties.

[0008]

The first aspect of the present invention is a high-density integral skin foam obtained by foaming a foaming composition containing a polyisocyanate, a polyol and water, wherein the polyol has at least 3 functional groups. ,
The polyether polyol having an average molecular weight of 6000 to 10000 and a polyether polyol having a functional group number of 2, which is obtained by randomly addition-polymerizing ethylene oxide, is used.
When the amount is 0% by weight, the ethylene oxide portion is 20% by weight or more, and when the total amount of the polyol is 100 parts by weight, the polyether polyol having the functional group of 3 is 60 parts by weight or more, It is characterized in that the polyether polyol having 2 functional groups is 10 to 30 parts by weight. The second invention is characterized in that the catalyst, which is one component of the foamable composition, contains at least an imidazole-based tertiary amine catalyst.

As the above-mentioned "polyisocyanate", those generally used as a raw material for polyurethane foam can be used without particular limitation. Examples thereof include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and modified products thereof. The above isocyanate component has an equivalent ratio of isocyanate groups to hydroxyl groups (referred to as an isocyanate index) of 0.8 to 1.3, particularly preferably 0.9 to 1.1.
It is used in the range of.

The above-mentioned "polyether polyol having 3 functional groups" is a polyether polyol obtained by reacting an alkylene oxide with a triol which is an initiator, and has "average molecular weight of 6000 to 10000". The alkylene oxide is usually propylene oxide and ethylene oxide is used in the form of a copolymer. Examples of triols include glycerin, trimethylolpropane, hexanetriol, triethanolamine and the like.

When the average molecular weight of the polyether polyol having 3 functional groups is less than 6000, the physical properties of the obtained integral skin foam, particularly the tensile strength, tensile elongation, tear strength, etc. are deteriorated, and the average molecular weight exceeds 10,000. When it is large, the viscosity of the polyol component becomes high, and the RIM
It is not preferable because a sufficient stirring effect cannot be obtained during molding and a good molded product cannot be obtained. Further, the amount of the polyether polyol having 3 functional groups to be used needs to be “60 parts by weight or more” when the total amount of the polyol is 100 parts by weight. It is not preferable because mechanical properties such as tensile strength of the Ruskin foam are deteriorated.

The above-mentioned "polyether polyol having two functional groups" includes an alkylene oxide (ethylene oxide and other alkylene oxides, usually propylene oxide) and a starting diol (water, propylene glycol, ethylene glycol, etc.). Which is obtained by randomly addition-polymerizing ethylene oxide, and the ethylene oxide portion is "when the polyether polyol having 2 functional groups is 100% by weight". 20% by weight or more ". The average number of functional groups of this polyol is 2
If it is larger, the viscosity of the polyol component becomes higher,
It is not preferable because it causes poor stirring during high-pressure stirring.

In addition, 20% or more of ethylene oxide must be randomly addition-polymerized with other alkylene oxides, and otherwise (for example,
If ethylene oxide is added to the end of the polymer of other alkylene oxides), the reaction may become too rapid and hinder molding. This is not preferable because problems such as deterioration occur. Further, in order to obtain a continuous and clear skin layer, the content of ethylene oxide needs to be 20% by weight or more, and when it is less than 20% by weight,
In addition to not being able to obtain a good skin layer, the foam becomes more foam-foaming as described above, and the shrinkage of the molded product after demolding is the same as the problem mentioned when using only water as the foaming agent of the prior art. There is also the problem of lower rates.

In order to form an integral skin layer in a foam by using water as a foaming agent as in the present invention, it is necessary to select a rapid reaction system, but if it is too rapid, the entire foam layer including the skin layer is selected. This causes a problem in moldability, and the reaction rate of the reaction system must be controlled. Therefore, in the present invention, it is preferable to use a tertiary amine-based catalyst containing at least an “imidazole-based tertiary amine” as the catalyst. In addition, 3 other than imidazole
It is more preferable to use a secondary amine-based catalyst in combination, because more stable moldability is maintained. The imidazole-based catalyst used here has the following characteristics, and is very useful when making an integral skin foam.

From the start of the reaction to the end (RT), the initial thickening is slow (between CT and GT) and then (GT).
(Between RT and RT), the curing speed is extremely fast, and therefore the excellent fluidity of the foamable composition is maintained and the curability is also excellent. RT: At the end of foaming, the rise time is abbreviated CT: Bubbles start to be generated, but when crosslinking is not performed, cream thyme is abbreviated GT: At the time of gelation, curing proceeds after this, a gel time abbreviation The cell's self-celling property becomes low, and the shrinkage rate of the molded product can be increased to the same level as that using the conventional freon-based foaming agent. In a system using water as a foaming agent, excellent adhesion with, for example, a metal as a core material of a steering wheel can be obtained.

As the imidazole-based tertiary amine catalyst, 1-methylimidazole, 1-ethylimidazole, 1-butylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1-isobutyl-2- Methyl imidazole, 2-ethyl-1,
4-dimethylimidazole, 1,2-diethyl-4-methylimidazole, 1- (2-hydroxyethyl) -2
-Methylimidazole, 1- (3-aminopropyl)-
2-methylimidazole, 1-benzyl-3-methylimidazole and the like can be mentioned, and as the tertiary amine type catalyst other than imidazole type, triethylenediamine, N
-Methylmorpholine, dimethylethanolamine, tetramethylpropylenediamine, dimethylcyclohexylamine, bisdimethylaminoethyl ether, dimethylpiperazine, triethylamine and the like.

These imidazole-based tertiary amine catalysts and tertiary amine catalysts other than the imidazole-based tertiary amine catalysts are not particularly limited, and one kind or a mixture of two or more kinds can be used. In addition, the imidazole-based tertiary amine catalyst has an amount of 0.1% when the total amount of the polyol and the crosslinking agent is 100 parts by weight.
It is preferable to use 5 to 3 parts by weight, and the tertiary amine catalyst other than the imidazole-based tertiary amine catalyst is preferably used in a ratio of about 0.2 to 0.5 with respect to the imidazole-based tertiary amine catalyst. By using each catalyst in the above range,
It is preferable because the reaction rate is appropriate for the formation of an integral skin layer, the cell foamability is low, and the shrinkage rate of the molded article is in an appropriate range.

Further, in the present invention, a tin-based metal catalyst such as dibutyltin laurate, dibutyltin maleate, dioctyltin laurate, or dioctyltin acetate may be used in combination with the amine-based catalyst, if necessary. Reduction of Amount of Amine Catalyst Used Since the catalytic activity of the metal catalyst is extremely high, the amount of amine catalyst used can be reduced. This not only solves the odor problem of amine-based catalysts (amine-based catalysts emit extremely strong amine odor), but also discolors vinyl chloride products called vinyl stain or fogging on the glass surface called fogging, which can be caused by amines. The phenomenon is suppressed. Also, cost reduction can be expected. Since the foam is highly curable, the molding cycle can be shortened. This improves productivity. Since the catalyst activity is highly temperature-dependent, the foaming inside the foam, which becomes hot during the reaction, is promoted, the reactivity on the mold surface at a relatively low temperature and a constant temperature is low, and it is a chemical foaming that uses water as a blowing agent. Nevertheless, an integral skin layer is formed. However, since tin-based metal catalysts have extremely high reactivity, are difficult to handle, and have the property of easily causing hydrolysis, it is necessary to fully consider such characteristics when using them.

[0019]

The integral skin foam is characterized by having an integral skin layer (dense layer) on the foam surface layer. More specifically, it is a polyurethane foam having a state in which the difference in density between the surface and the inside is continuously changing, and the density is high because there is almost no foaming near the surface layer, and the density gradually decreases toward the inside. It is what Due to such a structure, a conventional foaming agent is a so-called physical foaming agent (not a foaming agent that generates a gas by a chemical reaction or the like, but a foaming agent that becomes a gas body by a temperature rise or a pressure drop), specifically, CFC 11 Has been used exclusively. However, due to environmental problems, it is becoming impossible to use CFC-based foaming agents, and the use of chemical foaming agents that generate gas through a chemical reaction is being considered, but uniform foaming of the entire foam is unavoidable, and the use of an integral foam Difficult to form skin. In the present invention, only water, which is one of the chemical foaming agents, is used, but by using a specific amount of a specific polyol, an integral skin having the same structure and physical properties as those when using a freon-based foaming agent. I was able to get the form.

[0020]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. Examples 1 to 4 and Comparative Examples 1 to 2 Table 1 shows the composition of the foamable composition used in each Example and Comparative Example. In addition, the compounding amount of the components other than the polyisocyanate in Table 1 is 100% based on the total amount of the polyol component and the crosslinking agent.
It is expressed in parts by weight when it is defined as parts by weight. Polyisocyanate is represented by an isocyanate index. In addition, * means that it is out of the scope of the present invention.

[0021]

[Table 1]

The components shown in Table 1 are specifically shown below. (1) Polyol Component Polyol A: Asahi Glass Co., Ltd., trade name "EL-80"
4 "(hydroxyl value: 26, average molecular weight: 6500, number of functional groups: 3) Polyol B: manufactured by Sanyo Chemical Industries, Ltd., trade name" FA- "
908 "(hydroxyl value: 24, average molecular weight: 7,000, number of functional groups: 3) Polyol C: Sanyo Chemical Industries, Ltd., trade name" FA- "
703 "(hydroxyl value: 33, average molecular weight: 5000, number of functional groups: 3) Polyol a: Sanyo Chemical Industries, Ltd., trade name" PL- "
2100 "(ethylene oxide content: 31% by weight,
Hydroxyl value: 46, average molecular weight: 2000, number of functional groups:
2) Polyol b: Asahi Glass Co., Ltd., trade name "PML-50"
05 "(ethylene oxide content: 24% by weight, hydroxyl value: 28, average molecular weight: 4000, number of functional groups: 2)

(2) Crosslinking agent: ethylene glycol (3) catalyst component catalyst (1): 1-isobutyl-2-methylimidazole catalyst (2): bisdimethylaminoethyl ether catalyst (3): 1-methylimidazole catalyst ( 4): DBTDL (dibutyltin dilaurate) catalyst (5): 33% by weight solution of triethylenediamine in dipropylene glycol (4) blowing agent: water (5) other components: pigment (6) isocyanate X: 4,4'-MDI Prepolymer / Polymeric-MDI mixture (NCO% = 26%)

Using the foamable composition shown in Table 1 above, an integral skin foam was molded by the following method. 200 × 200, which was prepared by charging a polyol, a cross-linking agent, a foaming agent, other polyol components, and a polyisocyanate into a tank of a high-pressure foaming machine and controlling the temperature at 45 to 50 ° C.
Using a mold of × 5 mm, reaction injection molding was carried out at a discharge pressure of 150 kg / cm ² , a discharge rate of 140 g / sec, and a temperature of both components of 30 ° C. After molding, the product was taken out of the mold and allowed to stand at room temperature for 1 week to be subjected to a physical property test. Table 2 shows the evaluation results of the moldability of the foam, the physical properties of the obtained foam, and the like.

[0025]

[Table 2]

The evaluation of each item in Table 2 was performed by the following methods. (1) Viscosity measurement: B-type viscometer (2) Stirrability: Visual observation of foam cell condition,
Observe color unevenness (3) Moldability: Evaluation of mold release from the mold, initial strength by touching the finger, etc. (4) Skin layer thickness: Measured with a gauge by enlarging under the microscope field (5) Mold shrinkage Rate: The value obtained by subtracting the length of the marking line transferred on the product from the length of the marking line marked on the die, divided by the length of the marking line, and multiplied by 100. (6) Tensile strength And tensile elongation: JIS K6301

According to the results shown in Table 2, there is no great difference in viscosity between the polyol components of Examples and Comparative Examples, and moreover, Freon 1
Since 1 is almost the same as when the foaming agent is used, the stirring property and the moldability during molding are all good. However, in each of the examples, a skin layer having a thickness of 0.4 to 0.8 mm was formed, whereas in the comparative example, the skin layer was not formed at all, and it was found that an integral skin foam was not obtained.
Further, while the foams of the respective examples show a shrinkage ratio of 0.2 to 0.5% based on the size of the molding die, which is not much different from the case where the freon-based foaming agent is used, the comparative examples In the form of, it has rather expanded. In addition, tensile strength,
The tensile elongation is also slightly low in the comparative example, and it can be seen that the physical properties tend to be inferior. The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application.

[0028]

EFFECTS OF THE INVENTION In the present invention, although only water is used as a foaming agent, it is possible to obtain an integral skin foam having a clear skin layer, which has good stirring properties and moldability during foam molding. The product has excellent properties such as shrinkage and tensile strength.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area C08L 75:04

Claims (2)

[Claims] 1. A high-density integral skin foam obtained by foaming a foamable composition containing a polyisocyanate, a polyol, and water, wherein the polyol is a polyether polyol having at least 3 functional groups and an average molecular weight of 6000 to 10000. When,
Obtained by random addition polymerization of ethylene oxide, containing a polyether polyol having a functional number of 2,
When the polyether polyol having 2 functional groups is 100% by weight, the ethylene oxide portion is 20% by weight or more, and the total amount of the polyol is 100%.
An integral skin foam comprising 60 parts by weight or more of the above-mentioned polyether polyol having 3 functional groups and 10 to 30 parts by weight of the above-mentioned polyether polyol having 2 functional groups. 2. The high-density integral skin foam according to claim 1, wherein the catalyst that is one component of the foamable composition contains at least an imidazole-based tertiary amine catalyst.