JPS6049649B2 - Method for curing urethanes containing free isocyanate groups - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides unexpected improvements due to special compounds together with methylene dianiline complexes or racemic 2,3-di(4-aminophenyl)butane complexes with reduced curing times and significantly lower temperatures. This invention relates to a method of curing urethanes containing free isocyanates to produce urethane polymers with durable properties.

Traditionally, curing of amine-curable polymers or prepolymers, such as isocyanate-terminated polyurethane prepolymers, generally involves incorporating an amine curing agent, shaping the resulting mixture into a useful shape, and heating the resulting mixture. including completing the curing reaction. however,
A problem commonly encountered with this method has been premature reaction of the curing agent with the curable polymer during the mixing and molding operations. This problem was particularly likely to occur in highly reactive systems, such as in the curing of isocyanate-terminated polyurethane prepolymers. Such systems required the use of specialized short residence time mixers and specific diamine curing agents with low activity, which also generally limited the physical properties of the vulcanizing agent. A widely used type of curing agent that solves many of the above problems is a complex of methylene dianiline with a salt, which is generally heated at 100°C.
methylene dianiline is liberated from the complex upon heating above temperatures and initiates curing of the polymer (see US Pat. No. 3,755,261).

Despite improvements in the technology, such types of curing agents still tend to be time consuming, require undesirable demold times of the molded parts, and therefore require a large number of molds, which can be uneconomical. It was hot. The only way to overcome these drawbacks was to increase the curing temperature (which, of course, would increase the curing rate). however,
High curing temperatures caused greater thermal expansion and consequent shrinkage in the molded article, often causing distortion and cracking in the product. Recently, various curing agent complexes, such as methylene dianiline, have generally been promoted with various polar substances as well as hydroxyl group-containing compounds.

Although cure times are generally improved and cure temperatures are lowered, these various compounds have several undesirable aspects. For example, some compounds tend to cure too quickly. Therefore, uniform curing of molded products has been difficult. Another problem is that they act as solvents with automatic metering and mixing equipment! There was a tendency for this to occur and actually dissolve the various seals of the device. Outgassing was yet another problem in that the contacted compound tended to cure the polymer before the gas had time to escape from the molded article. Still other catalysts tended to produce viscous polymers, which required excessive time to mold in addition to degassing problems. On the other hand, many compounds created compositions with viscosities that were too low and created problems with accurate metering of the various ingredients due to slippage of the actual metering pump. In terms of physical properties, neither catalyst provided improved properties. It is therefore an object of the present invention to provide an improved method for curing urethanes containing free isocyanate groups.

That is, the present invention provides a method for curing urethanes containing free isocyanate in a reaction vessel, including the step of adding 100 parts by weight of urethane containing free isocyanate groups, and the step of adding 100 parts by weight of urethane containing 0.8 to 1.0 parts by weight based on the free active groups of the urethane. 2 equivalents of a salt selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, sodium nitrate, linium chloride, lithium bromide, lithium iodide, lithium nitrate and sodium cyanide and 4.4"-methylene dihydride. complexes with aniline and from sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, rubidium chloride, rubidium bromide, rubidium iodide, cesium chloride, cesium bromide and cesium iodide Salts selected from the group consisting of racemic 2,3-di(4-aminophenyl)
- a curing agent selected from the group consisting of complexes with butane in which the molar ratio of said dianiline or said butane to said salt in each said complex is about 3 to 1; and tetraethylene glycol di(2-ethyl hexoate), natrapropylene glycol di(2-ethylhexoate), tetrabutylene glycol di(2-ethylhexoate), tetrapentylene glycol di(2-ethylhexoate) diethylene dipropylene glycol di (2-ethylhexoate), and propylene-triethylene glycol di(2-ethylhexoate) from about 1.0 to about 15.0 parts by weight. We provide a method to do this.

According to the concept of the present invention, the use of various specific ester plasticizers in combination with the curing agent used for curing results in good demold times, particularly for casting urethane elastomers, which have a preferred application as tire body materials. , has been found to result in increased curing rates, lowered curing temperatures, or both, along with eliminating outgassing problems and unexpected improvements in physical durability properties.

A particular preferred curing agent is a complex of 4.4''-methylene dianiline (MDA) and a salt.

The preparation of that particular curing agent complex is described in U.S. Pat. No. 37,552.
It is described in the specification of No. 61. The description is especially 4.
Various complexes of 4''-methylene dianiline and salts and their preparation are hereby incorporated by reference.Complexes utilized as curing agents generally include:
There are reaction products of 4.4''-methylene dianiline and the following salts (ratio of about 3 moles of methylene dianiline to about 1 mole of salt): sodium chloride, sodium bromide, sodium iodide, sodium nitrate, chloride. Lithium, lithium bromide, lithium iodide, lithium nitrate and sodium cyanide. Sodium chloride is the highly preferred salt. Other complexes that can be used as curing agents are racemic 2,3-di(4-aminophenyl)butane and The reaction product is a ratio of about 3 moles of diamine to about 1 mole of salt with any of the salts listed below.

Sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, rubidium chloride, rubidium bromide, rubidium iodide, cesium chloride, cesium bromide and cesium iodide. A highly preferred salt is sodium chloride. The preparation of the curing agent is also described in US Pat. No. 3,755,261. The description thereof is incorporated herein by reference. When the preferred curing agents, dianiline complexes or butane complexes mentioned above, are utilized for curing urethanes, methylene dianiline is liberated from the complex when heated to a temperature of about 100'C, and the free methylene dianiline is used as a curing agent. Urethanes are cured in a manner believed to be identical to that which occurs when using aniline or butane.

The above complexes are also described in US Pat.
A number of amine curable prepolymers or polymers can be cured as described in US Pat.

The disclosure of US Pat. No. 3,755,261 is incorporated herein with respect to general and specific types of amine-curable prepolymers or polymers. Generally, a preferred class of such urethanes are those generally made by the reaction of diisocyanates with glycols or diols, generally having a molecular weight of from 400 to 8,000, preferably from 600 to 3,000. Such urethanes are typically prepared by reacting polyalkylene diols, polyalkylene ether diols, polyester polyols, polybutadiene diols, or combinations thereof with an equivalent or slight excess of diisocyanate or triisocyanate to form terminal isocyanate groups. can be made by forming a prepolymer with The present invention relates to such produced urethanes as well as other produced urethanes which will be fully apparent to those skilled in the art. Patent specifications describing general types of urethanes include U.S. Pat.
No. 3568, No. 2866774, No. 2900368, No. 2929800, No. 2948691, No. 294
No. 8707 and No. 3114735. Particular diols that are highly preferred include polypropylene ether diol and polytetramethylene ether diol.
Other preferred diols include polyethylene ether diol, polytriethylene ether diol, polyhexamethylene ether diol, and the like. It has been unexpectedly found that certain ester plasticizers of the present invention, when used in combination with the complex curing agents described above, act as accelerators or have a contact effect on the curing of polyurethanes.

In addition, when various polymers are cured in heated molds, such as in the manufacture of cast tire body materials, problems such as outgassing, premature curing, and failure often encountered with other catalysts for the complex curing agents mentioned above are also avoided. Uniform curing, slow feed rates into the mold due to high viscosity of the composition, and metering problems due to often unreasonably low viscosities generally do not occur. From about 1.0 to about 15.0 parts by weight of the ester of the present invention, based on 10 parts by volume of urethane, is preferred.

The preferred range is about 2.0 to about 10. This is the salivary part. Of course, the exact amount of a particular polyglycol will vary depending on the particular curing temperature, the particular urethane, and the particular catalyst of the invention. The esters used in the present invention include tetraethylene glycol di(2-ethylhexoate), tetrapropylene glycol di(2-ethylhexoate), tetrabutylene glycol di(2-ethylhexoate),
Tetrapentylene glycol di(2-ethylhexoate), diethylene-dipropylene glycol di(2-ethylhexoate)
ethylhexoate) and propylene-triethylene glycol di(2-ethylhexoate).

A highly preferred compound is tetraethylene glycol di(2-ethylhexoate). Its specific formula is as follows: Tetraethylene glycol di(2-ethylhexoate) is combined with Union ◆ carbide (UniO
It can be purchased as "FlexOl 4G0" manufactured by nCarbide.

The formulas of the other polyglycol esters of 2-ethylhexanoic acid are the same, except of course for the molecular parts within the antagonism.

As mentioned above, certain plasticizers in this group provide good practical results in the processing and curing of various urethanes. As is clear from the chemical formula of the representative compound above, the plasticizer is not extremely polar and does not contain free hydroxyl compounds like prior art compounds and the polar groups are considerably sterically hindered. The above fact is rather surprising since it is a high molecular weight ester. The plasticizers used in this invention generally have a high boiling point, for example tetraethylene glycol di(2-ethylhexoate) at 5 Torr.
It is also desirable that little plasticizer is lost during curing, in contrast to the volatile catalysts of the prior art, which are heated to 424° F. and thus tend to cause excessive shrinkage of the green form.

Furthermore, the viscosities of the various plasticizers (e.g. 12 Cp at 40'C for tetraethylene glycol di(2-ethylhexoate)) are suitable for accurate metering of the plasticizer component, i.e. without slipping of the metering pump. It is highly miscible when mixed with other ingredients such as urethanes and other plasticizers, yet allows fast injection times and favorable escape times for the gases generated. Therefore, uneven curing and outgassing problems are easily eliminated. Additionally, the plasticizers used in the present invention do not act as solvents or degrade the various rings and seals of forming and dispensing equipment. Further, the plasticizer is liquid over the desired curing temperature range of about 80°C to about 170°C. Preferred curing temperatures are from about 100 to about 140'C, with highly preferred temperatures from about 115 to about 125'C. The amount of the two curative complexes described above generally ranges from about 0.8 to about 1.2 diamines in the curative to free isocyanate groups in the polyurethane.
It is equivalent.

A more preferred range is about 0.9 to about 1.05 equivalents;
A ratio of 1.025 is highly preferred. Ratios higher or lower than the above general ranges in highly preferred products of cast urethane tire body materials result in significant differences both in the curing method of manufacture as well as in their physical properties. Conventional additives or compounds may be added to the compositions of the present invention to impart desired attributes or properties in accordance with well-known techniques in the art of forming and curing urethanes.

These include traditional antifoam agents, conventional pigments that impart desirable aesthetic appeal, and conventional fillers for foamed products. Of course, other additives such as flame retardants and the like may also be added depending on the desired product use. It is often desirable to add other conventional plasticizers to increase the flexibility of the product.

The addition of such conventional plasticizers is particularly preferred in applications as tire body materials. Certain preferred plasticizers utilized in the manufacture of urethanes include dioctyl phthalate (DOP), diisooctyl phthalate (DIOP)
, diisodecyl phthalate (DIDP), and dinonyl phthalate (DNP). Among these, DOP is extremely preferred. In addition to imparting increased flexibility to the final cured product, the use of conventional plasticizers as well as the ester plasticizers used in the present invention provides improvements as described in Examples 1 and 2 below. It has been unexpectedly found that this gives improved durability. Although the exact reasons for this result are not clearly understood, the utilization of conventional plasticizers in conjunction with the ester plasticizers used in the present invention provides a synergistic and unexpected It is thought that there is a tendency to act in such a way as to produce the following results. A suitable range for conventional plasticizers is from about 4 to about 2 parts per part (1) part of urethane;
Preferably from about 12 to about 17 parts. Since various ester plasticizers, such as the polyglycol ester of 2-ethylhexanoic acid, are completely miscible with the preferred plasticizers such as DOP and are less volatile than the plasticizers, the results obtained are lower. It is a volatile plasticizer system, thereby reducing gassing problems and retaining large amounts of the preferred plasticizer in the cured elastomer system. Furthermore, 2
The use of seed plasticizers provides greater elasticity to the cured polymer, especially at low temperatures. Preferably, conventional plasticizers are added as a mixture with amine hardeners. Light stabilizers may also be utilized, particularly for the production of polyurethane as cast timer material.

A desirable light stabilizer is about 0.3 to 100 parts of urethane.
Carbon black in an amount of about 3.0 parts. Amounts in excess of 3 parts create a very viscous polymer composition whereby quick or reasonable molding times are difficult, resulting in uneven curing and poor properties.

A fine particle size is desirable since carbon black with a large particle size tends to become a site of cracking. Typically, particles of 1 μm or less are preferred. Of course, any conventional carbon black meeting this requirement, such as Calxt
REGAL 400 manufactured by
You can use R. In addition, carbon black also provides the tire with a distinctive black color that may be aesthetically appealing to prospective purchasers. Other light stabilizers include from about 0.3 to about 1 per 1 (4) parts of polymer.
．． There is an amount of 5 parts of conventional inorganic or organic dyes or pigments.

Carbon black can be completely or partially replaced by a dye. In general, carbon black is desirable as opposed to dye;
Dyes are commonly utilized because they have a very small particle size, much smaller than μ. As a dye specifying agent, American Woojin (ArTlerjCanUgjne)
Thermoblast () is an organic dye sold by
Thermoplast NSP” and organic dye “Nigrosin” manufactured by American Cyanamid.
'0sine)SSB' is available. Of course, other conventional organic or inorganic dyes or pigments can also be used, such as TiO2. Polyurethanes made in accordance with the present invention can be used in shoe soles, clothing, roller wheels, automobile parts, and automobile pumpers.

As mentioned above, a very important and commercial application is in the production of tire body stock, which may be provided with conventional tread rubbers such as polybutadiene-styrene. The compositions of the present invention combine the urethane and the curing agent complex at ambient temperature or at a slightly higher temperature, such as about 50°C, but below the curing temperature of the complex curing agent, which is generally about 90-100°C. It can be made by mixing. Various additives, fillers, etc. can also be added and blended. When the plasticizer is the preferred complex of methylene dianiline and sodium chloride, it usually contains a protective colloid suspending agent such as lecithin. Lecithin is also a good foam stabilizer, but the formulated silicone compound, Tau Corning Paint Additive (DOwCOrning)
An antifoam agent such as paintAdditive #7 (DC-7) may be added. In general, it has been found that when using centrifugal casting, such as in the manufacture of tire body materials, it is not necessary to use an antifoaming agent if the overall viscosity is low and the molding speed is high. DOP can be utilized as a carrier for the MDA curing agent, so that the preferred plasticizer loading can be reduced accordingly. In any case, the various esters, such as the various polygolic esters of 2-ethylhexanoic acid, are added and mixed immediately before being dispensed into the casting mold. Desirably, short molding cycle times are desirable to reduce operating costs;
The viscosity of the urethane composition should preferably be less than 150 poise. Such a low viscosity further allows rapid mixing of the various components. A viscosity of 50 poise or less is preferred.

Molds are then filled and the composition is allowed to harden. The compositions of the present invention for tire body materials can generally be sufficiently cured within 5 minutes after being filled into a mold, so that they can be molded directly into molded articles by mechanical means without causing damage to the tire. Strong enough to withstand removal. Table 1 sets forth various physical properties of cast polyurethanes made in accordance with the present invention.

As is evident from Examples 1 and 2, the curing of the polyurethanes of the present invention clearly provides considerably higher durability properties than the control as well as an unexpected increase in the cure rate or an unexpected decrease in the cure time.

Example 1 Admiral Elastomer Processing for 3 components
Machine(AdmjralEIastOmerPrOce
ssingMachine) and mixed;
Three tires measuring 145-13 were centrifugally cast from the dispensed catalyst loaded elastomeric material.

Each of the three tires was cured for 1 hour at 120°C and then tested for durability in indoor rotation according to US Department of Transportation specifications.

1.9TWL(a). 075"" thick specimens were cured integrally with each tire for measurement of physical properties.

Furthermore, 15cTnX15CmX1.
Test plaques of 97 T$L (6″ x 6″″ x 0.075!″) were made. Two sets of these plaques were removed from the mold after only 5 minutes of pressurization time and then placed with the tire. Post-curing was performed in a circulating air oven at the times and temperatures indicated below for comparison of physical properties with integrally cured plaques.

The specified minimum total miles before failure according to Department of Transportation (D.O.T.) standards is 27,351wt (27,351wt) under severe conditions.
1,700 miles), whereas the subject tire has a mileage of 4,867 (3,025 miles) and 4,827-miles, respectively.
(3000 miles) and broke after 5301 km (3295 miles). D. for 145-13 tires. O
．． The Tl durability test was performed under rated load 5 and tire pressure [304 kg (6701b) per tire, 1.68 bar (24
psi)], with a stepwise increase in load as follows, maintaining a speed of 80 km/h (50 n1ph) throughout: 304 k9 (67 nph) without damage.
01b) for 4 hours [322i! (200 miles)], then increased the load to 338k9 (7451b) and 338k
9 (7451b) for 6 hours [483 km (300 miles)], then the load was increased to 363 kg (8001b), and at 363 kg (8001b) for 24T11 [19
Driving 31km (1200 miles).

After completing the specified 2735 km (1700 miles),
The subject test tires are damaged as follows: Tire 1: After 3735-(1700 miles), the load is reduced to 395h(
8701b) and at this load for 8 hours [644h(
400 manoil)] and the load was 443k9 (97
When the load was increased to 51b), it was operated for 8 hours [644h (400 miles)], and when the load was increased to 488k9 (10751b), it was operated for 8 hours [644kTt (400 miles)].

This tire was then 533k9 (11751
b) 201 krft (125 miles) [total 486
7-(3025 miles)] operated. Tire 2: Subject to the same load and speed conditions as Tire 1.
Next, with a load of 533k9 (11751b), 161km (
100 miles) [Total 4827-(3000 miles)
) was damaged after the operation. Tire 3: Under the same harsh conditions as Tire 1 and Tire 2, it was tested at 533k9 (11751b) and rated at 635kwL (3
95 miles) [total 5301km (3295 miles)
] It worked.

For comparison, a number of control tires had an overall average of 443k
9 (9751b) for 8 hours [i.e. 4022 in total]
km (2,500 miles)] and was damaged. The control tire formulation was the same as for Tires 1, 2 and 3, except that it did not contain any Flexol 4G0. It is therefore quite clear that a significant increase in durability has been obtained. Example 2 A D.C. with a minimum capacity of 0.5 Jf at 136.7 axes/hour (85 MPH). O. T. Two additional (145-13) tires were made in the same manner as Example 1 for testing at high speed specifications.

1.9 WU under various curing conditions for measurement of physical properties.
I1 (a). 075″″) was made in black. Of particular note is the excellent physical properties achieved in the high temperature tests of the black, which was removed from the mold after 5 minutes of pressure curing and then cured after 6 dusts at 120 DEG C. in a well-relaxed state.

145-13 tires subject D. O. T. The specific high speed test specifies a tire pressure of 1.68 bar (24 psi), a load of 304 k9 (6701b) per tire, and the following driving time and speed: 80.4 km/h (50 km/h).
MPH) 2. Warm up between C@, then increase speed to 120.6
km/hour (75 MPH) to 120.6 axes/hour (7
5MPH) and 0. time, then increase the speed to 128.7 krfL/hr (80 MPH) and increase the speed to 80 MPH.
80 MPH) for 0.5 hour, then reduce the speed to 136.
Increase to 715L/hr (85MPH).

The tire must pass the test without breaking.
Must be able to operate for 0.5 hours at 85 MPH. In the case of test tires 4 and 5, 136
．． The test continued as follows until failure exceeded 7km/hour (85MPH): 144.8!5t (90MPH)
So 0.

After 0.5A at 152.9h/hr (95MPH) for 5 hours and increasing the speed to 160.9km/hr (100MPH), both tires
MPH) and broke after 12 minutes.

For comparison, a number of control tires averaged 152.9kT.
Damaged during 01 Samurai at n/hour (95r1-4PH). The control tire had the same formulation as Tires 4 and 5, except that it did not contain any "Flexol 4G0". Although preferred embodiments have been illustrated and described in detail in accordance with patent law, it is understood that the present invention is not limited thereto and that the scope of the invention is to be determined only by the claims. It should be done.

Claims (1)

[Scope of Claims] 1. A method for curing urethanes containing free isocyanate in a reaction vessel, the step of adding 100 parts by weight of urethane containing free isocyanate groups; 0.8 to 1 part by weight based on the free active groups of the urethane. .2 equivalents of a salt selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, sodium nitrate, lithium chloride, lithium bromide, lithium iodide, lithium nitrate and sodium cyanide;
・Complex with 4'-methylene dianiline, and sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, rubidium chloride, rubidium bromide, rubidium iodide, cesium chloride, bromide A complex of a salt selected from the group consisting of cesium and cesium iodide and racemic 2,3-di(4-aminophenyl)-butane, the molar ratio of the dianiline or butane to the salt in each complex. curing agent selected from the group consisting of about 3 to 1, and tetraethylene glycol di(2-ethylhexoate), tetrapropylene glycol di(
2-ethylhexoate), tetrabutylene glycol di(2-ethylhexoate), tetrapentylene glycol di(2-ethylhexoate), diethylene-dipropylene glycol di(2-ethylhexoate), and An ester selected from the group consisting of propylene-triethylene glycol di(2-ethylhexoate) about 1.
A method comprising the step of adding 0 to about 15.0 parts by weight. 2. The method according to claim 1, wherein the curing agent complex is a salt of 4,4'-methylene dianiline and sodium chloride. 3. A method according to claim 1 or claim 2, characterized in that curing is carried out at a temperature of about 90 to about 170C. 4 the amount of ester is 2.0 to about 10.0 parts by weight;
4. The method of claim 3, wherein the amount of curing agent is from about 0.9 to about 1.05 equivalents.