JPH0138129B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing polyurethane foam with a hard skin. 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, reaction injection molding technology has developed,
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. In other words, when a molded product is removed from the mold in a short period of time, the skin may peel off, the foam may swell, or small voids may occur on the surface. The molded product must be kept in place. 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 these methods have the disadvantage that the fluidity of the foam decreases and the properties of the foam surface deteriorate. It was hot. Another disadvantage of conventional materials is that burrs generated during molding tend to remain on the mold surface. If burrs remain in the mold, it takes time to remove them, resulting in a longer molding cycle. Conventionally, no decisive method has been found to prevent burrs from remaining in the mold, that is, to prevent burrs from being attached to the molded product. The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to produce a polyurethane foam with a hard skin that prevents burrs generated during molding from remaining on the mold surface, has excellent surface properties and flowability, and can be demolded in a short time. The present invention provides a method for producing a polyurethane foam with a skin. The inventors have provided the following conditions when producing a hard-skinned polyurethane foam using RIM technology. (1) Mold temperature (2) Reactivity of the material, especially the polyol component, catalyst and foaming behavior, changes in hardness over time (3) Resin composition, especially the OH value of the polyol and the heat resistance of the resulting foam (4) Molding equipment In particular, as a result of examining methods of mixing materials, etc., a method for shortening the molding cycle was discovered and the present invention was achieved. Among these, the most important point in the present invention is to use a composition such that the glass transition point of the obtained foam skin is 100°C or higher, and to set the mold temperature to 55 to 80°C. The glass transition point of the foam skin is determined by the dynamic elastic modulus of the foam skin 1 to 2 mm (vibration wave: sine wave, vibration frequency: 10Hz,
It can be determined from the temperature at which the temperature rise rate (temperature increase rate: 1.5℃/min) starts to decrease rapidly. The dynamic elastic modulus (E) of the polyurethane foam skin with a hard skin is as shown in FIG. 1, and the glass transition point is Tg in FIG. Next, specific methods, limiting conditions, etc. for achieving the present invention will be described in more detail. That is, the polyurethane foam with a hard skin contains 20 to 80 wt% of an aliphatic amine polyol having a group represented by formula (1) in the molecule obtained by adding an alkylene oxide to an aliphatic amine; 80-20wt polyol derived from aromatic amine having a group represented by formula (2) in the molecule obtained by adding alkylene oxide to aromatic amine
% polyol mixture with an average OH value of 380 to 760 KOHmg/g, However, R, R': H or an alkyl group, n: a natural number, and Liquid A, which contains as essential components a blowing agent and a catalyst which is a salt of a tertiary amine, part or all of which has a heterocycle in the molecule, 4,4 ′-diphenylmethane diisocyanate,
B liquid containing polyphenylene polymethylene isocyanate or carbodiimidated polyphenylene polymethylene polyisocyanate as an essential component is impact-mixed at an isocyanate index in the range of 1.04 to 1.30, and this collision-mixed liquid is heated to a mold temperature of 55
It is obtained by injecting into a closed mold at ~80°C and foaming and curing in this closed mold. The average OH number of all polyols is 380-760KOH.
mg/g is used because if it is less than 380KOHmg/g, the glass transition point will be below 100℃, and the foam will easily swell during demolding, and if it is more than 760KOHmg/g, burrs will tend to remain on the mold surface. It's for a reason. The reason why the mold temperature is set at 55 to 80°C is that if it is lower than 55°C, burrs tend to remain on the mold surface, and if it is higher than 80°C, the skin layer density will be low and as a result, it will not be possible to obtain a strong molded product. It's for a reason. In addition, the amount of polyol obtained by adding alkylene oxide to the aromatic amine is 20 to 20%.
The reason why it is set at 80wt% is that if it is mixed at 20wt% or more, the hardness during demolding will be high and the molded product will be less likely to be damaged by the protruding pins.
This is because if the amount exceeds 80 wt%, the viscosity of the composition increases, making it impossible to perform sufficient impact mixing. In addition, since the time from mixing the composition of the present invention, liquid A, which contains a polyol as a main component, and liquid B, which contains a polyisocyanate as a main component, to gelation is extremely short, it is difficult to form a foam product. Well,
It is necessary to mix in a short time using a reaction injection molding machine. The conventional mixing method (mixing method using a low-pressure foaming machine) takes a long time to mix;
Further, since the mixing efficiency is low, even if the composition of the present invention is used, a good skinned foam cannot be obtained. The composition of the present invention is particularly effective when producing a hard foam with a skin, and from experience in producing conventional uniform foam bodies, semi-rigid foam bodies, and soft foam bodies, the composition of the present invention is effective. It is not possible to guess what the intention is. The method for manufacturing the hard polyurethane foam with skin of the present invention will be specifically explained below. First, FIG. 2 is a schematic diagram showing a liquid reflection molding apparatus for carrying out the manufacturing method of the present invention. When this device does not discharge stock solution, stock solution A containing polyol, blowing agent, and catalyst as main components stored in stock solution tanks 1 and 3,
After the stock solution B containing polyisocyanate as its main component is transported to the mixing head 8 by the high-pressure metering pump 6, it returns to the stock solution tanks 1 and 3 via the heat exchanger 5 connected to the temperature controller 11. When discharging, the mixing head is operated by the hydraulic unit 7, and the colliding and mixed stock solution is injected into the cavity 20 of the closed mold 10 placed between the clamping units 9. Next, the composition used in the method for manufacturing a skinned rigid polyurethane foam of the present invention will be specifically explained. Polyols obtained by adding alkylene oxide to aliphatic amines used in the present invention include alkylene oxide adducts such as monoethanolamine, triethanolamine, ethylenediamine, triethylenetetramine, ammonia, hexamethylenediamine, and diethylenetriamine. Examples of alkylene oxides include ethylene oxide (EO), propylene oxide (PO), butylene oxide, and epichlorohydrin. The above polyol can be obtained, for example, by reacting an aliphatic amine with an alkylene oxide under a basic catalyst. The polyol obtained by adding an alkylene oxide to an aromatic amine used in the present invention has a group represented by formula (2) in its molecule. (R, R': alkyl group, n: natural number) Specifically, it is an alkylene oxide adduct of 4,4'-diaminodiphenylmethane shown below. The above-mentioned polyols include commonly known polyether polyols and polyester polyols. Specific examples of these include glycerin, trimethylolpropane, pentaerythritol,
Polyols obtained by adding alkylene oxide to diglycerin, sorbitol, sucrose, diaminodiphenylmethane, tolylene diamine, xylylene diamine, phenol, etc. may be mixed as long as the present invention is not impaired.
“Polyurethanes Chemistry and
Technology，Part Chemistry，Part
Technology” Robert E. Krieger Publishing
Company, Huntington, New York1978,
Andlytical Chemistry of the by David Staly
Polyurethanes, Polyurethanes: Part”
Robert E. Krieger Publishing Company,
Huntington, New York 1979, and polyols described in "Plastic Materials Course (2) Polyurethane Resins" by Keiji Iwata, Nikkan Kogyo Shimbun, 1975 may be mixed within the range that does not impair the present invention. Isocyanates that can be used in the present invention include MDI (4,4'-diphenylmethane diisocyanate), which is obtained by reacting the reaction product of aniline and formaldehyde with phosgene. Isocyanate, that is, polyphenylene polymethylene polyisocyanate or carbon shown in formula (3) below. Ruboshiimidated MDI can also be used. Among these, carbodiimidized MDI, which is referred to by the Urethane Foam Industry Association as MDI and its analogues (including polymethylene polyphenylene polyisocyanate represented by the above formula (3)), is particularly effective. Specific examples of the catalyst, which is one of the most important materials used in the present invention, are shown below. Examples of tertiary amines with a heterocycle in the molecule include triethylenediamine, DBU [1,8-diaza-bicyclo(5,4,0)undec-7], and imidazole compounds, which contain nitrogen. Due to the ring structure, the direction of the unpaired electrons of nitrogen is fixed to some extent. The catalysts used in the present invention are these salts, which are
Acetic acid, formic acid, oxalic acid, propionic acid, phosphoric acid,
It can be obtained by adding a weak acid such as 2-ethylhexanoic acid, a strong acid such as nitric acid or hydrochloric acid, or a compound having a phenolic hydroxyl group such as phenol or cresol. In addition, the acids to be combined with the tertiary amine having a heterocycle in the molecule include Lewis acids and Breschewted acids in general. The above-mentioned tertiary amine can be used alone, but the following conventionally known catalytic compounds can also be used in combination with these. Specific examples include triethylenediamine,
dimethylethanolamine, morpholine compound,
Piperidine compounds, tin esters, etc.
Other examples are described in the aforementioned literature. Foam stabilizers include oxyalkylene copolymers of polydimethylsiloxane in general and fluorine-based surfactants in general. 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 important compounds in the present invention because they have the property of easily forming a tough skin. Other materials that can be used in the present invention include fillers, pigments, dyes,
There are flame retardants, ultraviolet absorbers, etc., and these also include the contents described in the above-mentioned literature. These materials can be blended into the polyol or polyisocyanate, or can be impact-mixed as separate components. Next, the outstanding features that occur when the composition of the present invention is used are shown below. FIG. 3 shows the foaming behavior of the foam in the case of free foaming, and FIG. 4 shows the change over time in the hardness (Shore D) of the foam surface. 21 and 23 are the measurement results when using the composition of the present invention, and 22 and 24 are the measurement results when using the conventional material. In this case, there is no difference in free foam density between the two compositions. The feature of using the composition of the present invention is that although the time until the foam starts to foam (the time until the foam starts to rise) [referred to as CT (cream time)] is long, the foam does not foam. Time to complete [RT
(referred to as rise time) is short, that is, RT/CT is large, and the rate of increase in hardness of the foam surface is slow. ,
This is thought to be the reason why the demolding time is short and a foam with excellent surface properties can be obtained. A specific example of the case where the composition is mixed and injected into a closed mold will be shown below. Unless otherwise specified, the content described below is based on the first
This is an example of the test performed using the equipment, conditions, and test method shown in the table. Further, the unit of the numerical value showing the blending ratio of the foam composition is parts by weight. (Example 1) A hard polyurethane foam with a skin was manufactured using the composition of Example No. 1 in Table 2 under the equipment and conditions shown in Table 1. As shown in Figure 2, a foam with excellent properties was obtained in a short time. Namely, 40 parts by weight of PO (propylene oxide) adduct of ethylenediamine (OH value: 540KOHmg/g), PO of 4,4-diaminodiphenylmethane
30 parts by weight of adduct (OH value: 430KOHmg/g), PO adduct of glycerin (OH value: 513KOHmg/g)
30 parts by weight, 1.0 parts by weight of oxyalkylene adduct of polydimethylsiloxane, 25 parts by weight of trichloromonofluoromethane, and 3.0 parts by weight of phenol salt of DBU [1,8-diazabicyclo(5,4,0)undecene-7]. Blending ratio of liquid A obtained by mixing and liquid B consisting of 133 parts by weight of crude MDI (NCO content: 30.5 wt%) (liquid B/liquid A, weight ratio)
Collision mixing was carried out using a high pressure foaming machine (RIM machine) at 1.16 to form a rigid polyurethane foam with a skin having an average density of 0.35 g/cm ³ . The average OH number of all polyols in this composition is 524.9 KOHmg/g, the reactivity (RT/CT) is 3.4, and the mold temperature is 55°C. When the demolding time was 2 minutes and 15 seconds, a foam with no blisters, cracks, or surface peeling was obtained, and when the demolding time was 2 minutes and 45 seconds or more, a foam with a particularly glossy surface was obtained. The surface hardness (Shor D) of the foam measured 3 minutes and 15 seconds after mixing the AB liquid showed a high value of 56. After the foam was left at room temperature for 24 hours, the measured glass transition point, bending strength, and bending modulus were as high as 113° C., 195 Kg/cm ² , and 72×10 ² Kg/cm ² , respectively. Furthermore, when the mold was removed in 2 minutes and 30 seconds, most of the burrs were attached to the molded product (form), and very little remained on the mold surface, making the mold extremely easy to clean. (Examples 2 to 15) Using the same method as Example 1, Example Nos. 2 to 15 in Table 2 were prepared.
When a rigid polyurethane foam with a skin was manufactured using the composition No. 15 under the equipment and conditions shown in Table 1, as shown in Examples 2 to 15 in Table 3, the foam with excellent properties could be produced in a short period of time. Obtained with. That is, these compositions had a low RT/CT, and even when demolded in a short time, there was no foam breakage or blistering, and the surface was glossy. Moreover, the hardness measured after 3 minutes and 15 seconds showed a high value. Furthermore, the glass transition point, bending strength, and bending modulus of elasticity all showed good values. Further, when the mold was removed in 2 minutes and 30 seconds, most of the burrs were attached to the molded product (form), with almost no burrs remaining on the mold surface, and the mold was extremely easy to clean. (Examples 16, 17, 18) Rigid polyurethane foam with a skin was manufactured using the compositions of Example Nos. 16, 17, and 18 in Table 4 under the equipment and conditions shown in Table 1. As shown in the Properties and Other column, a foam with excellent properties was obtained in a short time. That is, this composition:
RT/CT is small, and even when the mold temperature is set to 60, 70, and 80℃ and the mold is demolded in 2 minutes, 1 minute 45 seconds, and 1 minute 45 seconds, there is no foam destruction or blistering, and the surface is shiny. It was hot. Further, the hardness measured after 3 minutes and 15 seconds showed a high value, and the density uniformity of the foam was good. Furthermore, the glass transition point, bending strength, and bending elastic modulus all showed good values. Furthermore, even when demolded in a short time, as shown in Table 5, burrs were less likely to remain on the mold surface. (Example 19, 20) Example 16 using the compositions of Examples 19 and 20 in Table 4
When a rigid polyurethane foam with a skin was manufactured in the same manner as in Example 19 and 20 (the mold temperature was 70 and 80°C, respectively), it had excellent properties as shown in the properties column of Table 4. A suitable form was obtained in a short time. Furthermore, as shown in Table 5, these compositions had the property that burrs were less likely to remain on the mold surface even when demolded in a short time. (Comparative Examples 1 to 5) Using the compositions of Comparative Examples Nos. 1 to 5 in Table 5, skinned foams were manufactured in the same manner as in Example 1, ie, using the equipment and conditions shown in Table 1. The mold temperature is
The temperature was 48℃. The properties of the obtained foam were evaluated based on the measurement method shown in Table 1, and the results showed the values and properties shown in Table 6. Regarding the glass transition point, bending strength, and bending modulus, the values were almost the same as those of the examples, but when demolded in 3 minutes, comparative examples 1, 3,
Nos. 4 and 5 had blisters on the foam or lacked surface gloss. In Comparative Example 2, voids were observed on the surface. Furthermore, the hardness measured after 3 minutes and 15 seconds showed only a lower value compared to the example. The value of reactivity (RT/CT) was large. Another 2 minutes 30
When the mold was demolded in seconds, there were a lot of burrs left on the surface of the mold, and it took a lot of effort to clean the mold. (Comparative Examples 6 and 7) Using the compositions of Comparative Examples No. 6 and 7 in Table 7, Example
A foam was molded in the same manner as 23. However, the mold temperatures were 48°C and 85°C in Comparative Examples 6 and 7, respectively. The properties of the obtained foam were as shown in the Properties and Others column of Table 8. In other words, Comparative Example 6 is Example 23
The disadvantage was that burrs were more likely to remain on the mold surface compared to . Furthermore, Comparative Example 7 had the disadvantage that blisters or cracks occurred in the foam when demolded for a short time compared to Example 23, and only a foam with weaker strength was obtained. (Comparative Examples 8 and 9) Using the compositions of Comparative Examples 8 and 9 in Table 7, Example 16
The foam was molded in the same manner. The properties of the obtained foam were as shown in the Properties and Others column of Table 8. That is, Comparative Examples 8 and 9 had drawbacks such as blistering of the foam, cracking, and peeling of the surface when demolded in a short time. Furthermore, Comparative Example 9 had the disadvantage that burrs tended to remain on the mold surface.

【table】

【table】

[Table] *: Propylene oxide


**: Ethylene oxide


＊＊＊ :1,8-diazabicyclo(5,4,0)undecene-
7

＊＊＊＊: 4,4-diphenylmethane diisocyanate: Chemical formula

【table】

[Table] * 〓◎ The surface is glossy and good with no blisters, cracks, or peeling of the epidermis.

Claims (1)

[Claims] 1. A polyol derived from an aliphatic amine having a group represented by formula (1) in the molecule obtained by adding an alkylene oxide to an aliphatic amine.
80wt% and 80-20wt polyol derived from aromatic amine having a group represented by formula (2) in the molecule obtained by adding alkylene oxide to aromatic amine
A polyol mixture with an average OH value of 380 to 760 KOHmg/g consisting of However, R, R': H or an alkyl group, n: a natural number, A liquid whose essential component is a catalyst which is a salt of a tertiary amine having a heterocycle in the molecule, 4,4'-diphenylmethane diisocyanate, and polyphenylene. Collision mixing with liquid B containing nylene polymethylene isocyanate or carbodiimidated polyphenylene polymethylene polyisocyanate as an essential component to an isocyanate index in the range of 1.04 to 1.30,
Production of a polyurethane foam with a hard skin, characterized by injecting this collision-mixed liquid into a closed mold with a mold temperature of 55 to 80°C, and foaming and curing within this closed mold to produce a polyurethane foam with a skin. Method. 2. Claims characterized in that the polyol derived from the aliphatic amine is an alkylene oxide adduct such as monoethanolamine, triethanolamine, ethylenediamine, triethylenetetramine, ammonia, hexamethylenediamine, diethylenetriamine, etc. 2. A method for producing a skinned polyurethane foam according to item 1. 3. The method for producing a skinned polyurethane foam according to claim 1, wherein the polyol derived from the aromatic amine is an alkylene oxide adduct of 4,4'-diaminodiphenylmethane. 4. The method for producing a skinned polyurethane foam according to claim 1, wherein the blowing agent is water, trichlorofluoromethane, methylene chloride, or azobisisobutyronitrile. 5. A patent claim characterized in that the salt of the tertiary amine having a heterocycle is a salt of triethylenediamine, DBU [1,8-diaza-bicyclo(5,4,0)undec-7], or an imidazole compound. A method for producing a skinned polyurethane foam according to item 1.