JPS645528B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a hard urethane foam molded article with a skin. Rigid urethane foam molded products with skins have made great progress in recent years, particularly in the fields of home appliances, automobiles, and furniture. In general, hard urethane foam molded products with a skin are made by injecting an excessive amount of a hard urethane foam stock solution with a high expansion ratio into an airtight mold, and then foaming it to integrate the high-density skin layer and the low-density core layer. It is manufactured by molding, but when foaming is performed under normal pressure in the mold, the density distribution of the molded product becomes uneven, voids on the skin surface, and thermal conductivity increase.
In other words, there are problems such as poor insulation performance.
It has not yet been put into practical use. Among the above problems, uniform density distribution can be improved by injecting a large amount of urethane foam stock solution, but the density of the molded product increases and the thermal conductivity increases. In addition, voids that occur on the surface of the skin deteriorate the appearance and significantly reduce the commercial value of the molded product, but in general, the lower the foaming density of the injection stock solution, the lower the injection amount of the urethane foam stock solution. , occurs a lot. This can be improved somewhat by increasing the foaming density and the injection amount of the stock solution, but it is impossible to completely eliminate the voids at the end of the molded product. In addition, undesirable phenomena such as an increase in weight and an increase in thermal conductivity due to an increase in the density of the molded article are observed. In the case of a mold having a complicated shape, for example, a mold having uneven parts or insert parts, it is practically impossible to eliminate voids. In recent years, there has been a strong demand for lightweight molded products from the viewpoint of resource and energy conservation, and it is important to have low thermal conductivity, i.e., excellent heat insulation, uniform density of molded products, and no voids, even if it is not practical. There has been a strong demand from various quarters for a method of producing molded articles with an appearance in which the amount of molten metal is reduced to the extent that there is no oxidation. In view of these circumstances, the inventors conducted extensive research and found that, prior to injecting the hard urethane foam stock solution into an airtight mold, the pressure inside the mold was set to a specific pressure, while the hard urethane foam stock solution was injected into the airtight mold. The molded product has an excellent appearance, uniform density distribution, and excellent heat insulation performance by increasing the packing rate of approximately 150 to 450% and maintaining the temperature of the mold at approximately 10 to 45°C while the raw solution is foaming. The present invention was completed based on this knowledge. That is, in the present invention, after setting the pressure inside the airtight mold to about 50 to 500 mmHg, a hard urethane foam stock solution is injected into the mold so that the packing ratio is about 150 to 450%, and the temperature of the mold is lowered. This invention relates to a method for producing a hard urethane foam molded product with a skin, which is characterized by foaming while maintaining the temperature at about 10 to 45°C. The rigid urethane foam stock solution used in the present invention contains an organic polyisocyanate, a polyol, a catalyst, a blowing agent, a foam stabilizer, and if necessary, a flame retardant, a pigment, a stabilizer, and the like. As the organic polyisocyanate, those commonly used in producing ordinary rigid urethane foams can be used as they are.
Typical examples include toluylene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate (C-MDI), crude toluylene diisocyanate, and partially urethanized toluylene diisocyanate.
Examples include polyisocyanates modified by trimerization, carbodiimidization, amidation, or the like. Two or more of these may be used in combination. These polyisocyanates generally have NCO/OH equivalent ratios of about 1.03 to 1.15 relative to the aforementioned polyols.
It is preferable to use it within the range of . The polyol has a functional group number of about 2 to 8 and is used in the production of ordinary rigid urethane foam.
Polyether polyols, polyester polyols, etc. having a hydroxyl value of about 350 to 800 mgKOH/g can be used. In particular, an aromatic amine is used as an initiator, and ethylene oxide and propylene oxide are added thereto in a weight ratio of about 50 to 50/95 to 50, preferably about 10 to
Hydroxyl value approximately 300 to 550mgKOH/ obtained by adding blocks or randomly at a ratio of 30/90 to 70
g of polyether polyol A) and polyester polyol B) described below in a weight ratio of about 50 to
Those obtained by mixing in a ratio of 90/50 to 10, preferably about 60 to 85/40 to 15 are preferred. Aromatic amines used as initiators for polyether polyols A) include monoamines such as aniline and toluidine, such as phenylenediamine, O-tolylenediamine, m-tolylenediamine, naphthalenediamine, 4,4' - diamines such as diaminodiphenylmethane, xylene diamine, e.g. products obtained by condensation of aniline with formaldehyde, distillation residues such as tolylene diisocyanate and diphenylmethane diisocyanate, e.g. tolylene diisocyanate and diphenylmethane diisocyanate; Examples include decomposition products obtained by hydrolyzing urethane foam, etc., produced using, for example, alkali or amine. Two or more of these aromatic amines may be used in combination. The hydroxyl value of the polyether polyol (A) varies depending on the type of aromatic amine used, but is approximately 300 to 550 mgKOH/g, preferably approximately 350 to 550 mgKOH/g.
It is about 500mgKOH/g. Polyester polyol (B) is usually produced by condensing a polyol having a primary hydroxyl group with a polycarboxylic acid or a polycarboxylic acid anhydride. Examples of polyols having primary hydroxyl groups include ethylene glycol, diethylene glycol, triethylene glycol, 1,4 butanediol, 1,6 hexane glycol, trimethylolpropane, and pentaerythritol. Examples of polycarboxylic acids and polycarboxylic anhydrides include adipic acid, succinic acid, succinic anhydride, maleic acid, maleic anhydride, fumaric acid, phthalic acid, and pyromellitic acid. One or more of the above-mentioned polyols and one or more of polycarboxylic acids or polycarboxylic acid anhydrides under conditions of excess hydroxyl groups,
Obtained by heating, dehydration, and condensation. The hydroxyl value of this polyester polyol is usually about 300 to 500 mgKOH/g. When using a mixed polyol consisting of polyether polyol (A) and polyester polyol (B),
The proportion of the mixed polyol is approximately
It is preferable to use it in a proportion of 80% by weight or more, preferably about 90% by weight or more. Furthermore, the types and amounts of catalysts, foam stabilizers, and blowing agents used are not particularly limited, and can be used in accordance with conventional techniques. Typical examples of catalysts include tertiary amines such as dimethylethanolamine, triethylenediamine, tetramethylpropanediamine, tetramethylhexamethylenediamine, and dimethylcyclohexylamine, such as stannous octoate, dibutyltin dilaurate, etc. Examples include organic tin compounds. The amount of catalyst is usually about 100 parts by weight of polyol.
It is used in an amount of about 0.1 to 10 parts by weight. Examples of blowing agents include methylene chloride,
Chloroform, trichloromonofluoromethane,
Trichlorotrifluoroethane, tribromotrifluoroethane, dichlorodifluoromethane, etc., and particularly preferred are trichloromonofluoromethane and trichlorotrifluoroethane. The blowing agent is usually used in an amount of about 10 to 70 parts by weight per 100 parts by weight of the polyol. As the foam stabilizer, various siloxane/polyalkylene oxide block copolymers (silicon foam stabilizers) can be used. The foam stabilizer is usually used in an amount of about 0.2 to 3 parts by weight per 100 parts by weight of the polyol. In addition to the above-mentioned catalyst, blowing agent, and foam stabilizer, if necessary, for example, trichloroethyl phosphite,
Flame retardants such as trisdichloropropyl phosphate, chlorinated paraffin, tricresyl phosphate, pigments such as carbon black, titanium oxide, red iron oxide, phthalocyanine blue, such as 2-tetrabutylhydroquinone, phenylsalicylate, 2- An appropriate amount of a stabilizer such as hydroxyphenylbenzotriazole may be added. As the mold used in the present invention, any airtight mold made of a material normally used for synthetic resin molding can be used, but the material of the mold may be metal or metal and other materials. It is best to use a combination of materials. Further, it is preferable that the mold is equipped with a temperature regulator (eg, a built-in jacket for running cold and hot water), and is also provided with a valve for regulating the pressure inside the mold. In the present invention, first, the pressure inside the mold is reduced to approximately 50 to 500 mm.
Hg, preferably about 150-400 mmHg. The pressure inside the mold is arbitrarily selected depending on the type and amount of the blowing agent in the urethane stock solution used, the viscosity and curing characteristics of the rigid urethane foam stock solution, the temperature of the mold, etc. If the pressure inside the mold exceeds approximately 500 mmHg, unfilled areas may occur within the mold or the foam density may become non-uniform, as is the case with conventional normal pressure methods. If the pressure inside the mold is less than about 50 mmHg, the blowing agent may partially foam and roughen the cells inside the molded product. After setting the pressure in the mold to approximately 50 to 500 mmHg, the hard urethane foam stock solution is heated to a packing rate of approximately 150 to 450.
%, preferably about 180-400%. In particular, if you want a molded product with excellent strength and appearance, the packing rate is approximately 300 to 450%.
Furthermore, when a molded article with particularly low thermal conductivity is desired, the pack rate is preferably about 150 to 250%. Here, the pack rate is defined by the following formula. Packing rate (%) = Weight of stock solution required to obtain a hard urethane foam molded product with skin/Weight of stock solution required to completely fill the mold with hard urethane foam stock solution x 10
0 The hard urethane foam stock solution is injected by directly connecting the injection part of a high-pressure foaming machine to the injection port of the mold. After injecting the hard urethane foam stock solution into the mold, the temperature of the mold is set to about 10 to 45℃, preferably about 15 to 30℃.
Foam while maintaining at ℃. If the temperature of the mold exceeds approximately 45°C, only molded products with voids will be obtained. On the other hand, temperatures below 10°C are excellent in terms of voids and thermal conductivity, but the density distribution becomes uneven, unfilled areas occur in the mold, and the curing speed of the molded product is slow. Therefore, demolding time becomes long, which is disadvantageous for industrial production. According to the present invention, a hard urethane foam molded article with a skin having low thermal conductivity, a good appearance, and a uniform density distribution can be easily obtained, and therefore it is an industrially extremely advantageous method. The present invention will be explained in more detail with reference to Examples below. Example 1 Component A crude MDI (Millionate MR-200 manufactured by Nippon Polyurethane Co., Ltd.) 100 parts B component Γ polyether polyol 1 (aromatic diamine/
Propylene oxide/ethylene oxide hydroxyl value 400mgKOH/g) 35 parts Γ polyether polyol 2 (aromatic diamine/
Propylene oxide/ethylene oxide (hydroxyl value: 490mgKOH/g) 35 parts Γ polyester polyol (adipic acid, trimethylolpropane, diethylene glycol (hydroxyl value: 400mgKOH/g)) 17 parts Blowing agent trichloromorphoromethane (Showa Denko Frontier 11) 30 parts catalyst 1,4-diazabicyclo(2,2,2)octane
0.7 parts Foam stabilizer Polysiloxane polyoxyalkylene glycol polymer (Shin-Etsu Chemical Co., Ltd. Foam stabilizer F-318) 1.5 parts A and B components were mixed in a high-pressure foaming machine (PU-50;
The solution was charged into two tanks (manufactured by Polyurethane Engineering Co., Ltd.), and the temperature of each solution was adjusted to 20°C. The injection head of the foaming machine was directly connected to the lower mold as shown in FIG. 1, and then the upper and lower molds were closed and the temperature of the mold was adjusted as shown in Table 1 by circulating water whose temperature had been adjusted in advance. Next, the valve directly connecting the vacuum buffer tank and the mold was opened, and the pressure inside the mold was adjusted to a constant pressure as shown in Table 1. After the pressure in the mold reaches the target value, activate the high-pressure foaming machine, mix the A component/B component at a ratio of 120 parts/100 parts, and fill the stock solution in the mold with a pack rate of about 150 to 450%. Injected and foamed. After curing, the mold was opened to obtain a molded product.

【table】

[Table] Example 2 Molded products were obtained using the same stock solution, mold, and operating conditions as in Example 1, with a mold temperature of 20° C. and a mold pressure of 760 and 260 mmHg, with different pack rates. The results of the molded products obtained are shown in Table 2.

[Table] Note: Density distribution and appearance are the same as Table 1.
Thermal conductivity unit K〓′/mh℃

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a mold used when foaming a rigid urethane foam stock solution. 1...Injection machine, 2...Lower mold, 3...Upper mold, 4...
...Jiyun water pipe for mold temperature adjustment, 5...Vacuum damper, 6...Pressure reduction pipe, 7...Pressure adjustment valve,
8... Decompression buffer tank, 9... Type cavity, 1
0...Vacuum pump, 11...Injection film gate, 12...Vacuum fine passage within the cavity, 13
...Mold airtight packing between the upper mold, lower mold and injection head, 14...Pressure gauge.

Claims (1)

[Claims] 1. After setting the pressure inside the airtight mold to about 50 to 500 mmHg, pour the hard urethane foam stock solution into the mold so that the packing ratio is about 150 to 450%, and lower the temperature of the mold to about 10 to 45℃. A method for producing a hard urethane foam molded product with a skin, which is characterized by foaming while holding the foam.