JPS6245249B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Object of the Invention [Field of Industrial Application] The present invention relates to a fast-curing polyurethane elastomer composition that can be cured and removed from the mold in one to ten-odd minutes at room temperature or relatively low temperature. More specifically, by selecting an appropriate composition of the prepolymer and curing agent, especially the amount of chain extender and urethanization catalyst, the pot life at the time of mixing the prepolymer and curing agent can be adjusted from tens of seconds to several minutes. A fast-curing polyurethane elastomer composition that can be cured and removed from the mold at room temperature or relatively low temperature in a short time by stirring and mixing using a high-pressure to low-pressure injection machine, batch type stirrer, etc. depending on the pot life. Regarding. [Prior art] MOCA (3.3' TDI (tolylene diisocyanate) using -dichloro-4,4'-diaminodiphenylmethane) as a curing agent
Prepolymer type [using polytetramethylene ether glycol (hereinafter abbreviated as PTMEG), polyester diol, polyoxypropylene glycol (hereinafter abbreviated as PPG), etc. as the polyol], semi-one shot method, etc., uses glycol as a curing agent. There is a method using 1,8-naphthylene diisocyanate or diphenylmethane diisocyanate/polyester diol. However, TDI in raw materials causes bronchial asthma, eczema, etc., and aromatic amines such as MOCA have the risk of causing cancer, so their use has become a serious problem in terms of environmental health. Both methods had the major drawback of requiring several hours to cure at approximately 100° C. and were extremely difficult to work with. In addition, although it is possible to shorten the pot life when the prepolymer and curing agent are mixed by using a catalyst for either type, it is completely impossible to shorten the curing time to a few minutes. Due to the high viscosity of the prepolymer and the high melting point of MOCA, etc., it is necessary to raise the temperature of the raw material to around 100℃, and currently there are no high-pressure casting machines that can use such high-temperature raw materials. Even if such a casting machine were manufactured, it would be impossible to shorten the curing time to a few minutes. Now, regarding high-density polyurethane foam (also called microcellular elastomer) used for automobile parts such as shoe soles and bumper guards, the above-mentioned publications such as Special Publication No. 47-22711, No. 46-38587, No. 47-1386, etc. A method is disclosed that cures at lower temperatures and more quickly than so-called cast elastomers. All of these methods are carried out by the so-called one-shot method using modified MDI as the isocyanate. On the other hand, examples of fast-curing polyurethane elastomers include JP-A-49-118795 and JP-A-51-125199, which disclose the use of a prepolymer as an isocyanate.
also discloses the use of PTMEG in prepolymers and curing agents. However, it is very difficult to satisfy both fast curing properties and physical properties of the cured product using these methods, and it is difficult to satisfy both fast curing properties and physical properties of the cured product.
No elastomers with high physical properties comparable to those obtained with PTMEG/TDI prepolymers were obtained. [Problems to be solved by the invention] Therefore, the present inventors have developed a fast-curing and MOCA
As a result of intensive research in order to obtain an elastomer with high physical properties comparable to those of cast-molded elastomers such as the above-mentioned Adiprene L-100 manufactured by DuPont, which is cured under heating using Reduce its viscosity by selecting
Adiprene L-100 can be applied to a casting machine at room temperature to relatively low temperature, has remarkable fast curing properties, and
It has been discovered that an elastomer with high physical properties comparable to those of the present invention can be obtained, and the present invention has been achieved. (b) Structure of the invention [Means for solving the problems] That is, the present invention provides a mixture of (i) purified diphenylmethane diisocyanate (hereinafter abbreviated as MDI) and a carbodiimide-modified product of the compound which is liquid at room temperature. 4 to 6 equivalents and (ii) average molecular weight of 650 to 2000.
A prepolymer (A) which is liquid at room temperature and is made by reacting 1 equivalent of PTMEG alone or a mixture of PTMEG with an aliphatic diol having a molecular weight of 250 or less, 1 equivalent of the above PTMEG, 1 to 4 equivalents of diol as a chain extender, and an organic metal. a curing agent (B) consisting of a mixture of catalysts, -
A fast-curing polyurethane elastomer composition comprising NCO groups/-OH groups (equivalent ratio) of 1.00 to 1.10, preferably 1.03 to 1.07, which has a pot life when mixing (A) and (B). By adjusting the amount of catalyst, the mold can be cured and removed from the mold in 1 to 10-odd minutes at room temperature to a relatively low temperature of 40 to 60°C. In the present invention, the carbodiimide-modified product of MDI that is liquid at room temperature is
Refers to products manufactured by the method disclosed in 2908 etc. In addition, the above aliphatic diols with a molecular weight of 250 or less include propylene glycol (hereinafter abbreviated as PG),
These include dipropylene glycol (hereinafter abbreviated as DPG), diethylene glycol (hereinafter abbreviated as DEG), and the like. In order to produce prepolymer (A), 4 to 6 equivalents of a mixture of purified MDI and its carbodiimide-modified product are reacted with 1 equivalent of PTEMG alone or a mixture of PTEMG and the above aliphatic diol having a molecular weight of 250 or less. However, if the amount of the mixture used is less than this range, the viscosity of the prepolymer will increase,
In addition to making the molding operation difficult, the physical properties of the polyurethane elastomer, especially the impact resilience, are significantly reduced. If the amount exceeds this range, moldability deteriorates, demolding takes a long time, and minute cracks occur in the molded product. Next, the diol in the curing agent (B) is ethylene glycol (hereinafter abbreviated as EG), DEG, 1.4-
It refers to either butanediol or cyclohexanedimethanol, and it is necessary to use 1 to 4 equivalents of this diol. The reason for this is that if the amount used is less than this range, the strength of the polyurethane elastomer will not reach the required value, and if it is more than this range, the compatibility will decrease, resulting in poor moldability such as the occurrence of cracks, and the This is because compression set, which is a physical property, increases. Furthermore, the above-mentioned organometallic catalysts include those known as urethane catalysts, such as dibutyltin dilaurate (hereinafter abbreviated as DBTDL), lead octylate,
Cobalt naphthenate and the like are used. To explain in more detail the adjustment of the pot life when mixing the prepolymer and curing agent by the amount of the urethanization catalyst, for example, if the amount of DBTDL in 100 parts by weight (the following parts represent parts by weight) of a curing agent of a certain composition is If it is 0.008 parts, the pot life is 5 minutes, and if it is 0.03 parts, it is 1 minute.
The pot life can be easily adjusted by simply increasing or decreasing the amount of catalyst so that 0.1 parts per minute is about 20 seconds. (Note) Pot life means that after the two liquids start mixing,
This is the time it takes for the viscosity to rise to 1000ps and for the fluidity to almost disappear. The above-mentioned high-pressure casting machine uses high-pressure pumps such as axial piston pumps and bottle pumps to
A low-pressure casting machine is one that circulates the stock solution at a circulation pressure of ~200Kg/ ^cm2 , mixes the stock solution by colliding it in a small mixing head, and then casts it. The stock solution is sent to a mixing section using a low-pressure pump such as a gear pump, stirred and mixed using a rotor or static mixer, and then cast. Further, as the batch type stirrer, one that eliminates the inclusion of bubbles during stirring, such as Agitator (trade name, manufactured by Shimamura Seisakusho), is particularly suitable. [Function] In carrying out the present invention, the prepolymer (A) and curing agent (B) may be used at room temperature or heated to below about 60°C for the purpose of reducing viscosity, if necessary. Ru. In addition to various casting methods that can be applied to so-called cast elastomers, there are also casting methods that use a high-pressure casting machine.
It is also possible to apply the RIM (Reaction Injection Molding) method, and thick coating can also be performed using an airless spray machine or the like. [Example] Next, the present invention will be explained in more detail by giving examples and reference examples. Example 1 One equivalent of PTMEG with an average molecular weight of 1000 and MDI
Carbodiimide modification with NCO group content 29% by weight
MDI (liquid at room temperature, hereinafter abbreviated as liquid MDI)
5.4 equivalents of isocyanate mixed at a weight ratio of 7/3 were reacted at 80°C for 3 hours to obtain a prepolymer (C) with 14.8% free isocyanate groups and a viscosity of 2000 cps (25°C). On the other hand, 1 equivalent of PTMEG with an average molecular weight of 1000, 1.
2 equivalents of 4-butanediol and 0.05 g of DBTDL were mixed and used as a curing agent (D). After vacuum degassing the prepolymer (C) and curing agent (D),
Both liquids were thoroughly mixed using a stirrer for 1.5 minutes without entraining air bubbles at a compounding ratio such that the -NCO group/-OH group equivalent ratio was 1.05, and then heated in a heating furnace maintained at 60℃. It was cast into a mold for a 2 mm thick sheet. It took 5 minutes from the start of mixing the two liquids until the mixed liquid reached 1000 Ps, and the cured product showed no trapped air bubbles, cracks, etc., and could be demolded 10 minutes after the start of mixing the two liquids. The physical properties of the product are shown in Table 1. Adiprene L
-100 (manufactured by DuPont) showed physical property values comparable to those of an elastomer cured with MOCA. Example 2 A curing liquid prepared by mixing 1 equivalent of PTMEG with an average molecular weight of 1000, 2 equivalents of 1,4-butanediol, and 0.2 g of DBTDL was mixed with the prepolymer (C) obtained in Example 1 using a low-pressure casting machine (Toho Kikai AF). -206 type, using a gear pump with a maximum discharge rate of 3/min for both two liquids, and a foaming machine for urethane foam that mixes with a mixing rotor), the mixture ratio is such that the -NCO group / -OH group equivalent ratio is 1.05. While stirring and mixing the liquid, it was poured into a mold for a 2 mm thick sheet maintained at 50° C. at a discharge rate of 2 kg/mim. After the mixing head starts dispensing,
It took 1 minute to reach 1000 ps (25°C), and the cured product could be demolded in 5 minutes, and no bubbles or cracks were observed in the cured product. The physical properties of the product are shown in Table 1, and the physical property values were the same as in the case of batch stirring in Example 1. Example 3 A curing agent prepared by mixing 1 equivalent of PTMEG with an average molecular weight of 1000, 2 equivalents of 1,4-butanediol, and 0.6 g of DBTDL was mixed with the prepolymer (C) obtained in Example 1 using a high-pressure casting machine (Toho Kikai NR- 215 type, maximum discharge amount for both liquids
(7.5/min axial piston pump used)
-NCO group/-OH group equivalent ratio 1.05, discharge amount 7.5
Molding was carried out at kg/min (125 g/sec). After starting discharge from the mixing head, it took approximately 20 seconds to reach 1000 ps, and the cured product could be demolded in 1.5 minutes. A cured product free of air bubbles, voids, cracks, etc. was obtained. The physical properties of the cured product are shown in Table 1, and no major changes were observed compared to Examples 1 and 2. Example 4 An isocyanate mixture (NCO group content 32.6% by weight) 5.5 equivalents and 3 at 80°C.
time reaction, NCO group content 14.9% by weight, viscosity
A prepolymer (H) of 4100 cps (25°C) was obtained. A curing agent was prepared by mixing 1 equivalent of PTMEG with an average molecular weight of 1000, 2 equivalents of 1,4-butanediol, and 0.6 g of DBTDL. The prepolymer (H) and the curing agent were molded using a high-pressure casting machine at an -NCO group/-OH group equivalent ratio of 1.05, resulting in a molded product free of bubbles, voids, cracks, etc. The physical properties of the molded product are shown in Table 1. Comparative example 1 1 equivalent of PTMEG with average molecular weight 1500, MDI and liquid
7.1 equivalents of isocyanate mixed with MDI at a ratio of 7/3 by weight was reacted at 80°C for 3 hours,
A prepolymer (E) with a free NCO of 14.8% and a viscosity of 2800 cps (25°C) was obtained. The above prepolymer (E) and the curing agent obtained in Example 1 (D)
A casting test was conducted in the same manner as in Example 1 at an -NCO group/-OH group equivalent ratio of 1.05. After starting to mix the two liquids (E) and (D), it took 3.5 minutes for the viscosity of the mixed liquid to reach 1000 ps, and it took 20 minutes for demolding. Further, fine cracks were generated in a part of the cured product. The physical properties of the crack-free area were good as shown in Table 1, but as mentioned above, the moldability was poor, such as the demolding time being prolonged and cracks occurring. Comparative Example 2 1 equivalent of glycol with an average molecular weight of 500 by blending PTMEG with an average molecular weight of 1000 and DPG, and 3.6 equivalents of isocyanate with a weight ratio of 7/3 of MDI and liquid MDI were mixed at 80°C for 3 hours. After reaction, a prepolymer (F) with a free NCO of 14.8% and a viscosity of 7500 cps (25°C) was obtained. The above prepolymer (F) and the curing agent obtained in Example 1 (D)
A casting test was conducted in the same manner as in Example 1 at an -NCO group/-OH group equivalent ratio of 1.05. After starting mixing the two liquids, it took 5.5 minutes for the viscosity of the mixed liquid to reach 1000 ps, and 10 minutes for demolding. Although no bubbles or cracks were observed in the cured product, due to the high viscosity of the prepolymer,
It was necessary to increase the mixing time. Furthermore, as seen from the physical properties shown in Table 1, the impact resilience, which is a very important physical property of elastomers, was significantly reduced. That is, in Comparative Example 2, deterioration in moldability such as cracking did not occur, but deterioration in handling due to increased viscosity of the prepolymer, deterioration in physical properties of the elastomer, etc. were observed. Comparative Example 3 Hypren L-100 (trade name, manufactured by Mitsui Nisso Urethane Co., Ltd., NCO% 4.2, viscosity 18000 cps (25
A prepolymer made of PTMEG/TDI (equivalent to Adiprene L-100) of
After thoroughly mixing for 1 minute without bubbles at a -NCO group/-OH group equivalent ratio of 1.07 at 12.5° C., the mixture was poured into a mold in a heating furnace maintained at 100°C. The hardened elastomer was removed from the mold one hour after casting, and then placed in a 100°C oven for about 20 hours.
Post-curing was performed. Table 1 shows the physical properties of the elastomer after post-curing. (c) Effects of the invention

[Table] As can be seen from the above examples and Table 1,
By adopting the above-mentioned specific configuration, the present invention can produce a polyurethane elastomer with high purity and high physical properties without using either TDI or aromatic amine, and also accelerates the curing speed of the elastomer. This is useful because productivity can be significantly improved. Furthermore, since the well-known risks of TDI poisoning and carcinogenesis due to aromatic amines can be eliminated, the working environment will also be greatly improved.

Claims (1)

[Scope of Claims] 1 (i) 4 to 6 equivalents of a mixture of refined diphenylmethane diisocyanate and a carbodiimide-modified product of said compound that is liquid at room temperature; and (ii) polytetramethylene ether glycol having an average molecular weight of 650 to 2000 alone or This and molecular weight 250
A prepolymer (A) which is liquid at room temperature by reacting 1 equivalent of a mixture with the following aliphatic diol, 1 equivalent of the above polytetramethylene ether glycol, and ethylene glycol, diethylene glycol, 1,4-butanediol as a chain extender. , any one of cyclohexanedimethanol
~4 equivalents and a curing agent (B) consisting of a mixture of an organometallic catalyst at an equivalent ratio of -NCO group/-OH group of 1.00.
A fast-curing polyurethane elastomer composition formed by mixing in the range of 1.10 to 1.10.