KR840001192B1 - Rapid curing polyurethane elastomer - Google Patents

Abstract

Rapid curing polyurethane elastomers are prepd. by reacting diphenylmethane diiso- cyanate, 4-6 equivs. of carbodiamide modified polyurethane, 1 equiv. of polytetra- methylene ether glycol with an average m.w. of 650-2000, and/or aliphatic diol with a m.w. of 250 or less. The equiv. ratio of NCO/OH is 1.00-1.10 by blending the pre- polymer (A) with a hardner (B), which is composed of 1 equiv. of polytetramethylene, 1- 4 equiv. of diol with a m.w. of 250 or less, and an organic metal catalyst.

Description

Curable Polyurethane Elastomer

The present invention relates to a fast curable polyurethane elastomer. More particularly, the present invention relates to polyurethane elastomers which can be cured and demolded at relatively low temperatures and fast times. Molded polyurethane elastomers, which are widely used in rollers, belts, solid tires, etc., due to their excellent mechanical properties such as abrasion resistance and oil rejection, include two types, one of which is MOCA (3,3'-dichloro-4) as a hardener. , 4'-diaminodiphenylmethane), polyol polytetramethylene ether glycol (PTMEG) polyesterdiol, TDI (tolylene diisocyanate) prepolymer type used as polyoxypropylene glycol (PPG) and the other is 1,5-naphthylene diisocyanate or diphenylmethane diisocyanate / polyester diol systems are used and a form according to a semi-one shot process in which glycol is used as a curing agent. However, the process for both of the above mentioned forms has the drawback of having to cure for several hours at 100 ° C. and extremely low work efficiency.

In the two forms mentioned above, the pot life in mixing the curing agent and the prepolymer can be shortened by the use of a catalyst but it is impossible to shorten the curing time to moisture. Moreover, it is necessary to raise the temperature of the raw material to 100 ° C. or higher for the same reasons as high viscosity at the high melting point of the prepolymer of MOCA. However, high-pressure molding machines which can apply raw materials at such high temperatures are not available to date. If such a high pressure molder is available, it is not possible to shorten the curing time to moisture.

In high density polyurethanes, called micro-cellular elastomers and used for automotive parts such as soles and bumpers, Japanese Patent Application Nos. 211111/1972, 38587/1971 and 1386/1972 have a lower temperature than the above-mentioned template elastomers. A process that cures faster is described. In all the already described processes called single shot processes, an improved diphenylmethane diisocyanate (MDI) is used as the polyisocyanate.

For fast curable polyurethane elastomers, Japanese patent applications 118795/1974 and 125199/1976 have described the use of prepolymers as polyisocyanates, in particular the latter describes the use of PTMEG in prepolymers as a curing agent.

In the process described above, it is very difficult to simultaneously satisfy the physical properties of the fast cured and cured product, using MOCA as the curing agent, PTMEG / TDI prepolymers represented by Adiprene L-100 (E. Elastomers with good physical properties, such as those produced from Nemur End Company, have not yet been produced.

An object of the present invention is to mix 4-6 equivalents of a mixture of diphenylmethane diisocyanate with a carbodiimide modified material of the present compound that is liquid at room temperature and 1 equivalent of polytetramethylene ether glycol having an average molecular weight of 650-2000, or And a prepolymer (A), which is a liquid at room temperature, 1 equivalent of the polytetramethylene ether glycol, 1-4 equivalents of the diol having a molecular weight of 250 or less as a chain extender, and an organometallic compound. Mixing with a curing agent (B) consisting of a catalyst to provide a fast curable polyurethane elastomer is prepared so that the equivalent ratio of NCO / OH 1.00-1.10.

The present invention relates to a fast curable polyurethane elastomer that can be cured and demolded in a short time period of 1 to 10 minutes at relatively low temperatures such as room temperature. In particular, the present invention relates to fast curable polyurethane elastomers that can be cured and demoulded in a short period of time from room temperature to relatively low temperatures, wherein the polyurethane elastomer is a high pressure mold selected by a port life of prepolymer and hardener mixture. It is prepared by stirring mixing using a low pressure casting machine, a batch type stirrer, etc. The stirring is controlled from tens of seconds to several minutes by the selection of a prepolymer of a suitable composition and a curing agent, in particular by the amount of urea forming catalyst.

The present inventors hardened | cured by heating using MOCA. Extensive research has been carried out to obtain elastomers with excellent physical properties and fast curing properties of the melt-formed elastomers represented by iDupont-de-Mour and Company's Adiprene L-100, which can be applied to melting machines from room temperature to relatively low temperatures. It has been found that such elastomers can be obtained by satisfactory selection of prepolymer compositions so as to lower the viscosity.

The fast curable polyurethane elastomers of the present invention are 4-6 equivalents of a mixture of pure diphenyl methane diisocyanate and carbodiimide modified materials of the present compounds that are liquid at room temperature and 1 equivalent of polytetramethylene ether glycol having an average molecular weight of 650-2000. Or a mixture of these and aliphatic diols having a molecular weight of 250 or less, and a prepolymer (A), which is liquid at room temperature, 1 equivalent of the polytetramethylene ether glycol, diol having a molecular weight of 250 or less as a chain extender. It is prepared by mixing with 4 equivalents of a curing agent (B) composed of an organometallic catalyst such that the equivalent ratio of NCO / OH is 1.00-1.10, preferably 1.03-1.07, and the mixed phase port life of (A) and (B) is 10 By controlling the amount of catalyst from a few seconds to a few minutes, it can be cured and softened for one to ten minutes at a relatively low temperature from room temperature to 60 ° C.

Carbodiimide modified materials of MDI that are liquid at room temperature are prepared according to the processes described in Japanese Patent Application No. 4576/1963, 2908/1977 and the like.

Examples of aliphatic diols having a molecular weight of 250 or less include ethylene glycol (EG), propylene glycol (PG), dipropylene glycol (DPG), diethylene glycol (DEG), 1,4-butane-diol, cyclohexane dimethanol and bishydr Aromatic diols such as oxy ethoxybenzene, P-xylene-diol.

Examples of organometallic catalysts used include known catalysts for the formation of urethanes such as dibutyltindylate (DBTDL) leadoctylate, cobalt naphthenate. When describing in detail that the pot life is controlled by the amount of catalyst when mixing the prepolymer and the curing agent for forming a urethane, the pot life is increased or decreased by the amount of catalyst, that is, 0.05 parts DBTDL per 100 parts of the curing agent (hereinafter referred to as parts by weight). ), And pot life of 5 minutes, 1 minute and 20 seconds are obtained for 0.2 parts and 0.6 parts respectively. (Note) "Port Life" means the time from mixing two solutions until the viscosity increases to 1000 ps.

In the high pressure molding machine, the two solutions are circulated at a circulation pressure of 150 to 200 kg / cm3 using the storage solution axial pump and the Bosch pump, and the small amounts of these high pressure flows are mixed by collision mixing. do. In the low pressure molding machine, each raw material liquid is introduced into the mixing unit by a low pressure pump such as a gear pump, and then mixed by stirring with a rotary mixer, a stationary mixer, and the like. The batch type stirrer used is particularly preferably free of bubbles during agitation, such as Aziter (trademark of Shimadzaki Apparatus Co., Ltd.).

In the practice of the present invention, prepolymers (A) and curing agents (B) are used at room temperature or raised to about 60 ° C. in order to lower their viscosity as required. An example of a molding process that includes various molding processes that can be applied to a molding elastomer is a Reaction Injection Molding (RIM) process, in which a high-pressure molding machine is used. In this process, an air spraying machine is used to give an effect on thick coating. Can be.

Polyurethane elastomers produced by the process of the present invention are used in various fields such as rollers, belts, solid tires, automotive parts, coatings, linings and the like.

The invention is better illustrated by the methods of the following examples and comparative examples.

Example 1

A mixture of 1 equivalent of DTMEG and 5.4 equivalents of polyisocyanate having an average molecular weight of 1000 prepared by mixing MDI and carbodiimide-modified MDI (liquid at room temperature and then denoted liquid MDI) in a ratio of 7 to 3 The reaction was carried out at 3 DEG C for 3 hours to prepare a prepolymer (C) containing 14.8% free isocyanate radical and having a viscosity of 2000 cps at 25 DEG C.

On the other hand, curing agent (D) is prepared by mixing 1 equivalent of PTMEG, 2 equivalents of 1,4-butanediol and 0.05 g of DBTDL with an average molecular weight of 1000.

The prepolymer (C) and the curing agent (D) are vacuum degassed and the two solutions are mixed sufficiently for 1 minute 30 seconds using a stirrer at a mixing ratio of 1.05 NCO / OH equivalence ratio and the mixture is kept at 60 ° C. Mold in a 2 mm thick sheet in the oven. The time from the mixing of the two solutions until the viscosity of the mixture reaches 1000 ps is 5 minutes and the cured material is free of cracks and bubbles and can soften within 10 minutes after mixing the two solutions.

The physical properties of the product are shown in Table 1. children. It is like an elastomer made by curing Dupont de Nemours and Company's Adiprene L-100 with MOCA.

Example 2

The prepolymer (C) obtained in Example 1 was mixed with a hardener prepared by mixing 1 equivalent of PTMEG, 1,4-butane-diol and 0.2 g of DBTDL having an average molecular weight of 1000, and a low pressure molding machine (Toho Machinery Co., Ltd.). Type AF-206; a foaming machine for urethane bubbles in which a gear pump with a maximum discharge of 3 l / min is used for both solutions, the solution being mixed by a rotary mixer) and stirred so that the NCO / OH equivalence ratio is 1.05 The 2 mm thick sheet is molded by mixing and maintaining at 50 ° C. with a release rate of 2 kg / min. The time from the start of mold release until the viscosity reaches 1000 ps at 25 ° C. is 1 minute and the cured product can demould within 5 minutes and is free of cracks and bubbles. The product shows the same values of physical properties as in the case of batch stirring in Example 1 as shown in Table 1.

Example 3

The prepolymer (C) obtained in Example 1 was prepared by mixing 1 equivalent of PTMEG, 1,4-butane-diol and 2 equivalents of DBTDL 0.6 with an average molecular weight of 1000. The NR of Toho Machine Co., Ltd. -215 type; an axial piston pump with a maximum discharge of 7.5 l / min is used for both solutions), with an NCO / OH equivalent ratio of 1.05 and a discharge of 7.5 kg / min (125 g / sec). To be. The time from the start of the discharge from the mixer head until the viscosity reaches 1000 ps is about 20 seconds and the cured product can demould within 1 minute 30 seconds.

The cured product produced is free of cracks and bubbles. The physical properties of the cured product show little difference compared to Examples 1 and 2 as shown in Table 1.

Comparative Example 1

1 equivalent of PTMEG having an average molecular weight of 1500 and 7.1 equivalents of a polyisocyanate mixture prepared by mixing MDI and liquid MDI in a weight ratio of 7: 3 were reacted at 80 ° C for 3 hours to contain 14.8% of free NCO and at 25 ° C. A prepolymer (E) having a viscosity of 2800 cps is obtained.

The prepared prepolymer (E) and the curing agent (D) obtained in Example 1 were subjected to a mold test at an NCO / OH equivalent ratio of 1.05 in the same manner as in Example 1.

The time from the start of mixing the two solutions (E) and (D) until the viscosity of the mixture reaches 1000 ps is 3 minutes and 30 seconds and the demoulding takes 20 minutes.

Fine cracks are found in part of the cured product. The physical properties of the part without cracks are shown in Table 1, but the time for demolding the cured product is long and shows low formability such as enhancement of cracks.

Comparative Example 2

1 equivalent of a glycol mixture prepared by mixing PTMEG having an average molecular weight of 1000 with DPG such that the average molecular weight was 500, and 3.6 equivalents of a polyisocyanate mixture prepared by mixing MDI and liquid MDI in a ratio of 7: 3 by weight were 3 at 80 ° C. Time-reaction gives a prepolymer (F) containing 14.8% of free NCO and having a viscosity of 7500 cps at 25 ° C.

In Example 1, the curing agent (D) and the prepolymer (F) were subjected to a mold test with an NCO / OH equivalent ratio of 1.05 in the same manner as in Example 1.

The time from the start of the two solutions until the conduction of the mixture reaches 1000 ps is 5 minutes 30 seconds and takes 10 minutes to form.

Although there were no bubbles and cracks in the cured product, an extended mixing time was required to achieve high viscosity of the prepolymer. Elasticity, which is very important as the physical property of the elastic body, is very low.

According to Comparative Example 2, mold defects such as crack formation do not occur, but operational difficulties due to increased viscosity of the prepolymer and lower physical properties of the elastomer are shown.

Comparative Example 3

Hypron L-100 (prepolymer from PTMEG / TDI with a 4.2% NCO and a viscosity of 18,000 cps at 25 ° C under the trademark name of Misui-Nisso, complete with ediprene L-100) at 80 ° C After degassing, foaming is carried out using a method without foaming at 120 ° C. for 1 minute, followed by molding in an oven maintained at 100 ° C. with a mixing ratio of 100: 12.5, that is, an NCO / OH equivalent ratio of 1.07. . After 1 hour of the mold, the cured elastomer was demolded into a mold and subjected to post curing for 20 hours in an oven at 100 ° C. The physical properties of the elastomer obtained after the post cure treatment are shown in Table 1.

TABLE 1

Claims (1)

4 to 6 equivalents of a mixture of diphenylmethane diisocyanate and a carbodiamide modified substance of the present compound that is liquid at room temperature and 1 equivalent of polytetramethylene ether glycol having an average molecular weight of 650 to 2000, or an aliphatic diol having a molecular weight of 250 or less; It was prepared by reacting a mixture of these, consisting of a mixture of a prepolymer (A) which is a liquid at room temperature, 1 equivalent of the polytetramethylene ether glycol, 1 to 4 equivalents of a diol having a molecular weight of 250 or less as a chain extender, and an organometallic catalyst. Fast curable polyurethane elastomer prepared by mixing the curing agent (B) to be an NCO / OH equivalent ratio of 1.00 to 1.10.