JPH023695B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a method for manufacturing a molded product by reaction injection molding (hereinafter abbreviated as RIM), in which two liquid highly reactive liquids are collision-mixed and then reacted and cured in a mold. Urethane type Reinforced RIM (R-
Regarding the manufacturing method of molded products using RIM). Polyurethane-based RIM molding technology includes, for example, the company's elastomer molding technology for molding bumpers, etc., and hard urethane molding technology for molding equipment housings, etc.
It is broadly classified into RIM molding technology. The former is characterized by a technology for molding large molded products from liquid materials, and major advances have been recognized in improving the quality of molded products and shortening molding time. On the other hand, the latter hard urethane RIM
A major problem with molding technology is that it is difficult to shorten the molding time. In other words, unlike other plastic molded products, hard RIM molded products are lightweight, have a sense of volume (foam molding), and are relatively easy to paint, making them suitable for use as high-quality equipment housings, but the long molding time reduces productivity. is low. This is because the so-called demolding time from injecting the stock solution into the mold to demolding the product is long, so the total molding time becomes long. This demolding time is related to the thickness of the product, and in the case of elastomer RIM used to mold bumpers etc.
The thickness is several mm, so demolding time is short, but housings are characterized by their thick walls (voluminous feel), and the product thickness is often 10 mm or more, so demolding time is long. The polyurethanization reaction can be significantly faster with suitable catalysts, allowing curing in a few seconds, for example.
Since this is an exothermic reaction, internal heat buildup becomes extremely large in the case of thick-walled products. As a result, burns, cracks, etc. occur inside the product. If the reaction is controlled and demolded in order to prevent internal heat accumulation, the reaction is insufficient, the gel strength is low, and local expansion occurs due to the foaming pressure, making it impossible to obtain a satisfactory molded product. Therefore, in conventional methods, in order to avoid the occurrence of burns, cracks, etc., and to prevent local expansion, the reaction rate is reduced to suppress the amount of heat generated, and the mold is kept for a long time after demolding to prevent shape changes. The disadvantage is that it must be kept in a time type. Furthermore, conventional R-RIM technology only improves the thermal properties and some mechanical properties of molded products;
Electromagnetic properties (e.g. conductivity, electromagnetic shielding)
No consideration is given to adding value to the head. An object of the present invention is to provide a method for producing an R-RIM molded product that does not cause burns or cracks inside the molded product even when a highly reactive molding material is used, and that also shortens demolding time. Another object of the present invention is to provide a method for manufacturing R-RIM molded products with high added value that can be applied to new uses by greatly reducing the volume resistivity value. The present invention comprises (A) a polyurethane reaction injection molding material whose main raw materials are polyol and polyisocyanate as a matrix, (B) 5 to 50 parts by weight of short metal fibers added to 100 parts by weight of the reaction injection molding material, and (C ) Reaction injection molding characterized by performing reaction injection molding under conditions such that the maximum exothermic temperature of the molding material during molding is 120°C or less, and (D) obtaining a molded product with a volume resistivity value of 10 ⁴ Ω・cm or less. Pertains to the manufacturing method of molded products. In the present invention, a polyurethane RIM molding material whose main raw materials are polyol and polyisocyanate is used as a matrix. Various known polyol components can be used, such as polyoxyalkylene polyols, short-chain glycols, triols, polyols using aliphatic or aromatic amines as initiators, etc. One or two types of these can be used. The above can be used. As the polyoxyalkylene polyol, polyols normally used in the production of this type of polyurethane can be used, such as ethylene glycol, propylene glycol, glycols such as dimers and trimers thereof, glycerin, and trimethylolpropane. Examples include adducts obtained by adding alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide to polyfunctional alcohols such as triols, pentaerythritol, sorbitol, and seuucrose, and which have a viscosity of 500 cps or less at 25°C. Preferably. Examples of short-chain glycols and triols include ethylene glycol, propylene glycol, 1,
Examples of polyols using an aliphatic or aromatic amine as an initiator include 4-butanediol, glycerin, and trimethylolpropane. Examples include enylmethane, and adducts obtained by adding alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide to these. Examples of the polyisocyanate used in the present invention include 4,4'-diphenylmethane diisocyanate (MDI), polymethylene polyphenyl isocyanate (PAPI), Desmodyur L, Desmodyur 44V-20 (manufactured by Sumitomo Bayer), and Coronate L (Japan Polyurethane). ), Takenate D102 (Takeda Pharmaceutical Co., Ltd.), Isonate 143L (Kasei Upjiyon Co., Ltd.), Millionate MTL (Nippon Polyurethane Co., Ltd.)
etc. can be mentioned. In the present invention, the metal short fibers may be made of aluminum, aluminum alloy, copper, copper alloy, steel, stainless steel, cast iron, etc., and in particular have an average diameter of 10 to 600 μm and a length of 0.5 to 10 mm. Preferably. In the present invention, the shape of the metal is required to be fibrous, and using granular or plate metal is firstly difficult to perform RIM molding, and secondly, the effect of reducing thermal conductivity is small. be excluded by this. The thermal conductivity of short metal fibers made of any material is extremely high compared to that of the polyurethane material of the matrix.
It is preferably 10 times or more compared to 0.1 to 0.5 kcal/m・hr・℃, especially 7 kcal/m・hr・℃.
The temperature is preferably hr.°C or higher. Aluminum, aluminum alloy, and copper are preferable materials because of their high thermal conductivity. Next, the short metal fibers are mixed and dispersed in the matrix stock solution. The short metal fibers may be mixed with either the polyol component or the isocyanate component, or may be mixed with both. The specific gravity of both the polyol component and the isocyanate component is around 1, but the specific gravity of short metal fibers is 2.7 even for aluminum, which is the smallest, and after mixing
If stirring is not continued until RIM forming, the short metal fibers will settle and separate. Also from this point of view, short aluminum fibers are a preferable material. The mixing ratio of short metal fibers to the matrix is
It is preferably 5 to 50 parts, particularly preferably 10 to 30 parts, based on 100 parts by weight (the same applies hereinafter) of the matrix. In this range, the R-RIM stock solution remains liquid, and the thermal conductivity of the molding material during molding is high.
Rapid temperature rise due to exothermic reaction can be suppressed. Further, the volume resistivity of the obtained molded product is also small, which is preferable. In the present invention, the polyol and/or polyisocyanate component in which the short metal fibers are mixed and dispersed is used at an equivalent ratio of NCO/active hydrogen (hereinafter referred to as R).
The desired RIM molded product can be obtained by blending so that the ratio is about 0.95 to 1.2 and performing reaction injection molding. Molding can be done by normal methods,
For example, if necessary, a foaming agent may be added to the mixture of the above two components.
A catalyst and the like are added and reaction injection molded into a mold at a pressure of usually about 100 to 200 kg/cm ² . Examples of blowing agents include trichloromonofluoromethane, dichlorodifluoromethane, monochloromonofluoroethane, 1,1,2-trifluoroethane, 1,
Examples include 1,2,2-tetrafluoro-1,2-dichloroethane, methylene chloride, and monochloroethane. In addition, as a catalyst, dimethylbenzylamine, N
-Ethylmorpholine, triethylenediamine, dimethylenepiperazine, dimethylaminoethanol, triethanolamine, N,N,N',N'-
Tetramethylethylenediamine, N, N, N',
N'-tetramethylhexamethylene diamine, N,
Examples include amine compounds such as N,N',N'',N''-pentamethyldiethylenetriamine, and organometallic compounds such as dibutyltin diacetate, dibutyltin dilaurate, stannath octoate, and the like. In the present invention, the thermal conductivity of polyurethane, which is the matrix, is as low as 0.1 to 0.5 kcal/m・hr・℃, so if the exothermic reaction of urethanization is large, more heat is stored inside the molded product than is transferred to the mold. .
Although it is possible to suppress heat generation and increase gel strength by selecting the type of polyol component and isocyanate component of the polyurethane raw material, the effect is small and it is difficult to make significant improvements. According to the method of the present invention, since the thermal conductivity of the short metal fibers is significantly higher than that of the matrix, it is possible to reduce the maximum heat generation temperature during molding to 120° C. or lower. In the present invention, the maximum exothermic temperature is 120
By keeping the temperature below °C, the above-mentioned problems during molding can be solved and demolding time can be significantly shortened. Furthermore, in the present invention, electrical and electromagnetic properties can be added to the molded product by adding short metal fibers. That is, polyurethane generally has a volume resistivity of about 10 ¹³ to 10 ¹⁴ and is an insulating material, but in the method of the present invention, the volume resistivity of the obtained molded product can be reduced to 10 ⁴ Ω・cm or less. It can be made into a nearly conductive area. As described above, in the present invention, by increasing the thermal conductivity of the molding material during molding, it is possible to reduce internal heat accumulation even if it is highly reactive, and as a result, there is no burning or cracking inside the molded product, and as a result, rapid It is possible to increase gel strength and shorten demolding time. The method of the present invention can be applied not only to hard urethane RIM molding but also to elastomer RIM molding, and can be particularly advantageously used in the former hard urethane RIM molding. As a specific example, it can be used for housings, covers, panels, etc. in the fields of electromagnetic shielding housings, electrical equipment, computers, etc. Further, although it may be used alone, great effects can be obtained by applying a conductive paint. Reference examples and examples of the present invention will be described below. The polyol, polyisocyanate, and short metal fibers used were as follows. <Polyol> Polyol Takeda Pharmaceutical Co., Ltd., amine-modified polyol, Actol GR-30, OH value =
400KOHmg/g Polyol Made by Mitsui Toatsu Chemical Co., Ltd., polyfunctional polyol, Su450LA, OH value = 448KOHmg/g <Polyisocyanate> Made by Nippon Polyurethane Industries Co., Ltd., Millionate
MTL (hereinafter abbreviated as MTL), NCO content = 29.0wt
%

[Table] Reference Example 1 A homogeneous mixture of polyols and polyols in a ratio of 80/20 was heated and dehydrated under reduced pressure while passing nitrogen gas. 50g of this mixed polyol and MTL63.5
(NCO Index 1.20) were brought to a liquid temperature of 30°C, mixed, stirred, defoamed, and cast into a stainless steel container at 30°C. Reaction temperature measurements were taken at the center point of the vessel. Two minutes after the start of mixing, the temperature of the mixed liquid, which was at 50°C, rose significantly, and after curing at 104-124°C, reached a maximum temperature of 137°C. Reference Examples 2 to 5 A-1, A-2, C-1, which had been heat-dried in advance, was added to the mixed polyol obtained by the same formulation as Reference Example 1.
27 g of each C-2 was mixed and the same operation was performed to measure the maximum temperature of heat generated by the reaction, and the following results were obtained. It is clear that both temperatures are lower than the maximum temperature of Reference Example 1.

[Table] Reference Example 6 100g of mixed polyol with the same mixing ratio as Reference Example 1
and MTL126g and A-1 (108g) were mixed and defoamed,
Pour into a plate mold with a thickness of 2 mm, heat to 60℃, and heat to 50℃.
A pressure of Kg/cm ² was applied, and the mold was removed after 10 minutes to obtain a plate-shaped molded product. A disk-shaped test piece with a diameter of about 100 mm was cut out from this plate-shaped molded product, and the volume resistivity value measured according to the method of JIS K6911 was 5 x 10 Ω·cm. Example 1 Polyol 40Kg, polyol 10Kg and A-
1 (27Kg) and foam stabilizer (Toray Silicone).
Add 0.5 kg of SH-193) and 0.2 kg of tertiary amine (PC-9, manufactured by Sunabott) as a catalyst, mix with a propeller type stirrer, and then add 2 kg of monochlorotrifluoromethane as a blowing agent and mix.
- Pour into a designated tank directly connected to the RIM forming machine. This is called component A. On the other hand, MTL is R-
Pour into the other tank directly connected to the RIM molding machine. This is called component B. Next, the temperature of both A component and B component is adjusted to 30℃, and the mold size, which was previously adjusted to 50℃, is 500×
For 1 equivalent of component A into a mold of 500 mm and 25 mm thickness,
The discharge amount was set so that the B component was 1.2 equivalents.
RIM molding machine (manufactured by Klaus Matsufei, RIM
Using a dosing unit for RU-80 and R-RIM), both A and B components are collided, mixed, and injection-molded in a predetermined amount at a discharge pressure of 150 kg/cm ² . After casting, the molded product was left in the mold for 5 minutes and taken out, and there were no defects, and even when left at room temperature, no change in shape or localized blistering was observed. This molded product was cut and the cross section was observed, but no local burns or cracks were observed. In addition, when we measured the temperature by protruding a copper/constantan thermocouple inside the mold, the maximum temperature was
It was 98℃. Example 2 Polyol 40Kg, polyol 10Kg and A-
1 (20Kg), add 0.5Kg of foam stabilizer (Toren Silicone SH-193) and 0.2Kg of tertiary amine (PC-9, manufactured by Sunabbot) as a catalyst, mix with a propeller type stirrer, and then foam further. Add 2 kg of monochlorotrifluoromethane as an agent and mix.
Pour into a designated tank directly connected to the RIM molding machine,
This is called component A. On the other hand, MTL (63.5Kg) and A
-1 (20Kg) with a propeller type stirrer, R-
Pour this into the other tank directly connected to the RIM molding machine and use it as component B. Next, the temperature of both the A component and the B component is adjusted to 30℃, and the gold size, which has been adjusted to 50℃ in advance, is 500×
For 1 equivalent of component A into a mold of 500 mm and 25 mm thickness,
The discharge amount was set so that the B component was 1.2 equivalents.
RIM molding machine (manufactured by Klaus Matsufei, RIM
Using a dosing unit for PU-80 and R-RIM), both A and B components are collided, mixed, and injection-molded in a predetermined amount at a discharge pressure of 150 kg/cm ² . After casting, the molded product was left in the mold for 5 minutes and taken out, and there was no damage, and even when left at room temperature, no change in shape or local blistering was observed. No burns or cracks were observed in the cross section of this molded product. A disk-shaped test piece with a diameter of approximately 100 mm and a thickness of 2 mm was cut out from the molded product, and the volume resistivity value obtained by the method of JIS K6911 was 2×10 ³ Ω·cm.
When temperature was measured by protruding a thermocouple inside the mold, the maximum temperature was 89°C.

Claims (1)

[Claims] 1. (A) A polyurethane reaction injection molding material containing polyol and polyisocyanate as main raw materials as a matrix, (B) 5 to 50 parts by weight of short metal fibers per 100 parts by weight of the reaction injection molding material. In addition, (C) reaction injection molding is performed under conditions such that the maximum exothermic temperature of the molding material during molding is 120°C or less, and (D) a molded product with a volume resistivity value of 10 ⁴ Ω・cm or less is obtained. A method for producing reaction injection molded products.