JPS6332085B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition for producing a skinned rigid polyurethane foam. Polyurethane foam with a skin, which is obtained by mixing isocyanate, polyether containing active hydrogen, a blowing agent, a catalyst, etc., and then foaming and curing in a closed mold, is used in electrical and electronic equipment because of its excellent heat insulation, sound absorption, and strength. Suitable for use as parts materials and building materials. In recent years, with the development of reaction injection molding technology (RIM technology), the uses of the above-mentioned foam bodies are increasingly expanding. However, one factor limiting the industrial use of this aerated urethane product is the long molding cycle, especially the demolding time (from injecting the composition into the mold to ejecting the molded part). time) is long. That is, when the molded product is removed from the mold in a short period of time, the foam swells due to the foaming pressure, so the molded product must be held in the mold for a long time. Conventionally known methods for shortening demolding time include:
There are methods such as increasing the amount of catalyst blended, blending a highly active catalyst, and increasing the liquid temperature, but in these cases, the fluidity of the foam decreases and the surface properties of the foam deteriorate. There were flaws. Furthermore, it is known that by converting polyisocyanate into a prepolymer, heat generation during molding can be suppressed and demolding time can be shortened. However, this method has disadvantages in that the storage stability of the polyisocyanate decreases, the viscosity increases, and the heat resistance of the obtained foam decreases. The object of the present invention is to avoid the drawbacks of the above-mentioned prior art.
The resin composition for manufacturing hard polyurethane foam with a skin that can be demolded in a short time is characterized by the use of a polyol polymerized with polyisocyanate, which lowers the maximum exothermic temperature during molding and reduces the temperature during demolding. suppresses molded product blistering phenomenon,
The aim is to shorten demolding time. Specifically, the above resin composition is a prepolymerized polyol with an OH value of 350 to 800 KOH mg/g (this polyol is hereinafter referred to as polyol (A)), and a polyisocyanate (hereinafter referred to as polyisocyanate). , polyisocyanate (B)
) at an NCO/OH molar ratio of 0.05 to 0.3; a reaction accelerator for polyurethane production; a blowing agent; a foam stabilizer; and a polyisocyanate (hereinafter referred to as polyisocyanate). isocyanate (C)) as an essential component. This resin composition has good storage stability, and by using it, a rigid polyurethane foam with a skin that has excellent mechanical and thermal properties can be molded in a shorter time than ever before. It is something. Hereinafter, the resin composition of the present invention will be explained in more detail, and the process for producing the foam will be explained. Polyols (A) used in the present invention include polyether polyols and polyester polyols. Specific examples of these include glycerin, trimethylolpropane, ammonia, monoethanolamine, triethanolamine, pentaerythritol, sorbitol, sucrose, phenol,
Tolylene diamine, 4,4'-diaminodiphenylmethane, xylylene diamine, hydrogenated 4,4'-
There is a polyether polyol obtained by adding an alkylene oxide to diaminodiphenylmethane or the like. There is also a polyester polyol obtained by adding an alkylene oxide to an ester compound (carboxyl terminal) obtained by reacting phthalic anhydride with propylene glycol or ethylene glycol. Polyols other than those listed above include
“Polyurethanes” by J.Saunders, K.C.Frish
Chemistry and Technology, Part I
Chemistry, Part Technology” Robert E.
Krieger Publishing Company, Huntington,
New York 1978, “Analytical” by David Staly
Chemistry of the Polyurethanes,
Polyurethanes: Part” Robert E, Kriger
Publishing Company, Huntington, New
York1979, Keiji Iwata, “Plastic Material Structure”
There is a polyol described in "(2) Polyurethane Resin" Nikkan Kogyo Shinkaisha 1975. Particularly important among these are polyols obtained by adding alkylene oxide to aromatic amines represented by the following general formula (1). (However, R, R': H or an alkyl group, n: a natural number) Specific examples of the aromatic amine polyols include alkylene oxide adducts of 4,4'-diaminodiphenylmethane and alkylene oxide adducts of tolylene diamine. Considering the viscosity of the polyol, the heat resistance of the resulting molded product, and the balance of mechanical properties, the proportion of the aromatic amine polyol in the polyol (A) is preferably 20 to 80% by weight. desirable. Here, polyol (A)
The OH value needs to be 350 to 800 KOHmg/g. The reason is that the OH value is 350KOH.
If it is less than mg/g, the mechanical properties of the obtained molded product will be poor, and the foam will swell due to heat generated during molding, making it difficult to shorten the demolding time as intended by the present invention. This is because it disappears. On the other hand, OH
If the OH value is greater than 800 KOHmg/g, the obtained molded product will become brittle and an industrially effective product will not be obtained, so the OH value must be 800KOHmg/g or less. The polyol (A) may be a single polyol or a mixture of various polyols. In the case of a mixture, it is sufficient that its average OH value satisfies the above conditions. As a specific example of the polyisocyanate (B) used in the present invention, MDI (4,
4'-diphenylmethane diisocyanate), but not only MDI alone, but also similar isocyanates, such as polyphenylene polymethylene polyisocyanate, carbociimidized MDI
can also be used. Furthermore, the same applies to xylene diisocyanate, isophorone diisocyanate, and tolylene diisocyanate (TDI), including the compounds described in the aforementioned literature. Among these, the particularly important polyisocyanate (B) is a TDI compound represented by the following general formula (2), and an MDI compound represented by the following general formula (3). (However, l: 0.2 to 0.8) The prepolymerized polyol in the present invention comprises the above polyol (A) and polyisocyanate (B).
It can be obtained by reacting at an NCO/OH molar ratio of 0.05 to 0.3. Specifically, polyol (A) is heated to 25 to 80°C, polyisocyanate (B) is added dropwise with good stirring, and after the dropwise addition is completed, the reaction is completed by further stirring for 1 to 6 hours. Obtainable. In this case, polyol (A)
Even if it contains water, there is no problem as long as the amount is 1.5% by weight or less. Furthermore, if necessary, various reaction accelerators may be added for the purpose of accelerating the prepolymerization reaction. The end point of the reaction is the point at which the isocyanate content in the polyol becomes zero, and this can be measured by applying commonly used analytical methods. Specific examples of the reaction accelerator, foaming agent, and foam stabilizer used in the present invention will be described below. First, examples of reaction accelerators include various tertiary amine compounds and tin compounds. Specific examples of tertiary amine compounds include triethylenediamine, dimethylethanolamine, morpholines, piperazines, imidazole compounds, DBU (1,8-diaza-bicyclo(5,4,0)undecene-7),
alkylaminosilane, etc., and their salts, such as acetate, formate, oxalate, phosphate, 2-ethylhexanoate, phenol salt,
Cresol salts, hydrochlorides, etc. can also be used. On the other hand, tin compounds include dibutyltin dilaurate,
Dibutyltin diacetate. Other reaction accelerators that can be used in the present invention include compounds described in the above-mentioned books. In addition to water, blowing agents include low-boiling organic liquid compounds such as trichlorofluoromethane and methylene chloride, and compounds that decompose to generate nitrogen gas such as azobisisobutyronitrile. By changing this amount, foams with different densities can be obtained. Among these, halogenated hydrocarbons having a particularly low boiling point (0 to 60°C) are particularly valuable compounds in the present invention because they have the property of easily forming a tough skin. Foam stabilizers include oxyalkylene copolymers of polydimethylsiloxane in general and fluorine-based surfactants in general. The polyisocyanate (C) used in the present invention is preferably a diisocyanate or a triisocyanate, but may also contain polyfunctional isocyanates higher than these. Specific examples include hexamethylene diisocyanate, m-xylene diisocyanate, m-phenylene diisocyanate, tolylene diisocyanate, MDI,
Examples include polyphenylpolymethylene polyisocyanate. Among these, particularly effective polyisocyanates
(C) is an MDI polyisocyanate represented by the following general formula (3). (However, l: 0.2 to 0.8) This is because the obtained foam has good reactivity and heat resistance, and is also inexpensive. In addition, the blending amount of polyisocyanate (C) is
The amount is preferably such that the NCO/OH molar ratio is from 0.9 to 1.2. Other materials that can be used in the present invention include fillers, pigments, dyes, flame retardants, ultraviolet absorbers, etc., and these also include the contents described in the above-mentioned book. Next, a method for obtaining a hard polyurethane foam with a skin using the composition of the present invention will be explained. The above foam is prepared by mixing the composition of the present invention and injecting it into a sealed mold kept at a temperature of 40 to 80°C.
It can be manufactured by foaming and curing. However, in the composition of the present invention, after mixing the prepolymerized polyol and the polyisocyanate (C),
Since the time until gelation is extremely short, when molding the foam, an R liquid containing a reaction accelerator, a blowing agent, a foam stabilizer, and other auxiliary materials as necessary is mixed into the prepolymerized polyol. It is necessary to prepare a P liquid made of polyisocyanate (C) in advance, and mix both liquids using a high-pressure collision mixing type foaming machine. Therefore, since the conventional mixing method (mixing method using a low-pressure foaming machine) requires a long time for mixing and has low mixing efficiency, it is not possible to obtain a good skinned foam using the composition of the present invention. I can't. The composition of the present invention is particularly effective when producing a hard skinned polyurethane foam, and from the experience of producing conventional uniform foam bodies, semi-rigid foam bodies, and soft foam bodies, the present invention It is not possible to guess what is intended. Hereinafter, a method for manufacturing a hard polyurethane foam with a skin using the resin composition of the present invention will be specifically explained with reference to the drawings. The figure is a schematic explanatory diagram of a liquid reaction injection molding apparatus for producing a skinned rigid polyurethane foam using the composition of the present invention. In this device, when the stock solution is not discharged, the stock solution A containing prepolymerized polyol, a blowing agent, and a catalyst as the main components, and the stock solution B containing polyisocyanate as the main components stored in the stock solution tanks 1 and 3 are pumped through a high-pressure metering pump 6, 6 to the mixing head 8, it returns to the stock solution tanks 1 and 3 via the heat exchangers 5 and 5 connected to the temperature controller 11. On the other hand, when discharging the stock solution, the hydraulic unit 7 The mixing head 8 is operated, and the collided mixed stock solution is transferred to the cavity 2 of the closed type 10 placed between the clamping units 9.
It is designed to be ejected within 0. When the resin composition of the present invention is used in such an apparatus, a hard polyurethane foam with a skin having a density of 0.1 to 0.6 g/cm ³ and a thickness of 3 to 30 mm can be produced in a short time. The obtained foam is particularly effective for manufacturing various electrical equipment parts, automobile parts, and audio equipment parts that require heat insulation, sound absorption, weight reduction, and the like. The present invention will be explained in more detail below with reference to Examples. The contents described below are examples based on the equipment, molding conditions, and measuring methods shown in Table 1, unless otherwise specified. Further, the unit of the numerical value showing the blending ratio of the foam composition and the prepolymerized polyol is parts by weight. First, an example of manufacturing a prepolymerized polyol used in a foam manufacturing example will be described, and then an example of foam manufacturing will be described. Production example of prepolymerized polyol Production of prepolymerized polyol a The polyol shown in column (a) of Table 2, that is,
PO (propylene oxide) adduct of 4,4'-diaminodiphenylmethane (OH value: 450

【table】

【table】

【table】

[Table] Mix 60 parts by weight of glycerin PO adduct (OH value: 600KOHmg/g) with 40 parts by weight (KOHmg/g), and mix 60 parts by weight of the mixed solution (average OH value: 540KOHmg/g).
℃ and added MDI isocyanate (l=0.6; NCO content: 30.5% by weight)
13 parts by weight of was added to the mixture while stirring well, and the mixture was stirred for 3 hours to produce prepolymerized polyol a. NCO/OH moleization is 0.1.
The method of Siggia et al. (References: A. Farkas, J. Am.
Chem.Soc.82, 642 (1960)) was used to analyze isocyanates in prepolymerized polyol a.
No residual isocyanate was detected. Production of prepolymerized polyols b ₁ , b ₂ , b ₃ , C, and d As shown in columns (b), (c), (d), (e), and (f) of Table 2, each polyol In the same manner as for prepolymerized polyol a, polyisocyanate is added to prepolymerized polyols b ₁ , b ₂ ,
b ₃ , c, and d were produced. b ₁ , b ₂ , b ₃ , c, d
The NCO/OH blending molar ratio is 0.06, 0.15, and
They are 0.20, 0.15, and 0.28. There was no residual isocyanate in these prepolymerized polyols. Production of prepolymerized polyol e 100 parts by weight of the mixed polyol shown in column (a) of Table 2 was maintained at 60°C, and 8.4 parts by weight of TDI isocyanate (NCO content: 48% by weight) was added thereto. , and stirred for 6 hours to produce prepolymerized polyol e. The NCO/OH blending molar ratio is 0.1. Isocyanate in prepolymerized polyol e was analyzed by the method of Siggia et al., but no residual isocyanate was detected. Foam Manufacturing Examples Example 1 Using the composition shown in the Example 1 column of Table 3,
With the equipment and molding conditions shown in Table 1, the density is 0.35g/
A rigid polyurethane foam with a skin of cm ³ was produced.

【table】

[Table] That is, 113 parts by weight of prepolymerized polyol a and 10 parts by weight of trichlorofluoromethane as a blowing agent.
parts by weight, 0.5 parts by weight of H ₂ O, 2.0 parts by weight of alkylene oxide modified polydimethylsiloxane as a foam stabilizer, 3.0 parts by weight of triethylenediamine as a reaction accelerator.
Parts by weight, DBU [1,8-diazabicyclo(5,
4,0) Undecene-7] Add 0.1 part by weight,
The R solution was prepared by stirring well at room temperature. The above R liquid and P liquid consisting of 4,4'-diphenylmethane diisocyanate (NCO content: 31% by weight; l = 0.6) are mixed, foamed, and hardened under the equipment and molding conditions shown in Table 1 to obtain a density. A flat plate with a weight of 0.35 g/cm ³ and a thickness of 2 cm was molded. Blending ratio (weight ratio) of R liquid and P liquid
was performed with R:P=100:114. The maximum exothermic temperature during molding, demolding time, and mechanical properties were as shown in the column of Example 1 in Table 4. In other words, the maximum exothermic temperature is as low as 145℃.
The demolding time was as short as 120 seconds. Also, bending strength and Izotsu impact value (without notch)
are 180Kg/cm ² and 8.0Kg・cm/cm ² respectively.

[Table] Both showed high values. Examples 2, 3, 4, 5, 6, 7, 8 A hard polyurethane foam with a skin was produced in the same manner as in Example 1 using the compositions shown in the columns of Examples 2 to 8 in Table 3. Molded. The density, maximum heat generation temperature during molding, demolding time, bending strength, and Izot impact value of the obtained molded product are as follows:
They were as shown in columns 2 to 8 of Table 4. That is, no matter which composition is used,
The maximum exothermic temperature during molding was low and demolding time was short. Furthermore, both bending strength and Izot impact value showed good values. Example 9 100 parts by weight of prepolymerized polyol e, 10 parts by weight of trichloromonofluoromethane, 0.5 parts by weight of H ₂ O,
Alkylene oxide modified polydimethylsiloxane
2.0 parts by weight of triethylenediamine, 1.0 parts by weight of triethylenediamine, 0.1 parts by weight of dibutyltin dilaurate, and 1.0 parts by weight of carbon black were added and mixed well to prepare R liquid. A hard polyurethane foam with a skin was molded using the R liquid and the P liquid shown in Table 3 at a blending ratio (weight ratio) of 100:116 using the equipment and molding conditions shown in Table 2. The density of the obtained molded article was 0.35 g/cm ³ and the maximum exothermic temperature during molding was 149°C. The demolding time is as short as 125 seconds, and the bending strength and Izotsu impact value of the molded product are 175Kg/cm ² and 7.5Kg・cm/, respectively.
cm ² , a good value. Comparative Example A hard polyurethane foam with a skin was molded under the same conditions as in Example 1. However, the polyol used was one that had not been prepolymerized. As a result, the maximum exothermic temperature during molding was higher than in Example 1, and the demolding time was longer than in Example 1. The contents will be explained in detail below. A polyol consisting of 40 parts by weight of PO adduct of 4,4'-diaminodiphenylmethane and 60 parts by weight of glycerin PO adduct, 10 parts by weight of trichlorofluoromethane as a blowing agent, 0.5 part by weight of H ₂ O, and a foam stabilizer. 2.0 parts by weight of alkylene oxide-modified polydimethylsiloxane, 3.0 parts by weight of triethylenediamine as a reaction accelerator, and 0.1 part by weight of DBU/phenol salt were added to prepare an R liquid. Using this R liquid and P liquid consisting of 4,4'-diphenylmethane diisocyanate (MDI) system (NCO content: 31% by weight; l = 0.6), the density A rigid polyurethane foam with a skin of 0.35 g/cm ³ was molded. The blending ratio (weight ratio) of R liquid and P liquid was 100:126. In this case, the maximum exothermic temperature during molding was as high as 160°C, and the demolding time was as long as 200 seconds. The bending strength and Izod impact value of the molded product are respectively
168 Kg/cm ² and 7.2 Kg·cm/cm ² , both of which were lower than those of Example 1. As specifically stated above in the Examples and Comparative Examples,
By using the composition of the present invention, a hard skinned polyurethane foam with excellent mechanical properties can be molded in a short time. Therefore, the molding cycle can be significantly shortened compared to the conventional method, and production efficiency can be dramatically improved.

[Brief explanation of the drawing]

The figure is a schematic illustration of a liquid reaction injection molding apparatus for producing a skinned rigid polyurethane foam using the composition of the present invention. 1, 3... Stock solution tank, 8... Mixing head, 11... Temperature controller, 10... Closed type.

Claims (1)

[Claims] 1. As a prepolymerized polyol, an OH value of 350
~800KOHmg/g (210~ in terms of average molecular weight)
Polyol (A) consisting of polyol (480) and polyisocyanate (B) at an NCO/OH molar ratio of 0.05 to
A resin for producing a rigid polyurethane foam with a skin, characterized in that the essential components are: a product obtained by reacting at a ratio of 0.3; a reaction accelerator for polyurethane production; a foaming agent; a foam stabilizer; and polyisocyanate (C). Composition. 2. The skin according to claim 1, wherein 20 to 80 weight percent of the polyol (A) is a polyol obtained by adding alkylene oxide to an aromatic amine represented by the following general formula (1). Resin composition for manufacturing hard polyurethane foam. However, R, R': H or alkyl group n: natural number 3 The polyisocyanate (B) is a 4,4'-diphenylmethane diisocyanate (MDI) compound represented by the following general formula (3), (However, l: 0.2 to 0.8) The resin composition for producing a hard polyurethane foam with a skin according to claim 1. 4 The above polyisocyanate (C) is a 4,4'-diphenylmethane diisocyanate (MDI) compound represented by the following general formula (3), (However, l: 0.2 to 0.8) The resin composition for producing a hard polyurethane foam with a skin according to claim 1.