DE2248751C3 - Process for the preparation of polycarbodiimides with terminal urethane groups - Google Patents

Description

The invention relates to a process for the preparation of polycarbodiimides with terminal urethane groups. Stabilize the products obtained in this way excellent polyester urethane rubbers and peroxide-cured hydrocarbon rubbers against hydrolytic degradation. The method according to the invention relates to the reaction of arylene diisocyanates in which the isocyanate groups are of unequal reactivity, optionally with the use of Arylene diisocyanate with isocyanate groups of the same reactivity, carbodiimide-forming catalysts and a stoichiometric deficit of alcohols from the group of primary and secondary aliphatic alcohols, and is characterized in that

a) the above arylene diisocyanates, with a stoichiometric deficit in the ratio of alcoholic hydroxyl groups to isocyanate groups in the range from 1: 4 to 1:40 of the alcohols the group of primary and secondary aliphatic alcohols are implemented, so that not all Isocyanate groups are converted into urethane groups, and

b) carbodiimide-forming catalysts mixed in and the partially urethane-terminated arylene diisocyanates to polycarbodiimides with terminal Urethane groups are polymerized.

Carbodiimides are a well-known class of compounds and have widespread use as stabilizers for rubbers, plastics, and other materials found. Polymeric carbodiimides have found special use as stabilizers against hydrolytic degradation in polyester urethane rubbers. Polymeric carbodiimides are generally treated by polymerizing a diisocyanate obtained with phospholene oxide catalysts. Lots limited storage stability, for reasons not are fully known, but are believed to have some relation to the free terminal isocyanate groups that remain on the polycarbodiimide molecules.

So far, attempts have been made to improve the storability of polymeric carbodiimides in that they are treated with a primary or secondary aliphatic alcohol to free the isocya to convert natgruppen into urethane groups. Special in US Pat. No. 2,941,983 the manufacture is a polycarbodiimide with urethane end groups so described that a linear polymer with terminal diisocyanate or isocyanate groups with a

is carbodiimide-forming catalyst is implemented and the degree of polymerization is regulated by adjusting the volume of the emitted during the polymerization Carbon dioxide monitored When a pre-calculated amount of carbon dioxide evolved is reached the polymerization is stopped by a primary or secondary aliphatic alcohol enters into the reaction mixture by the remaining

Convert isocyanate groups into urethane groups. The resulting polycarbodiimide with urethane terminated

groups is limited to a relatively low molecular weight range, and when monitoring the The greatest care must be exercised in the amount of carbon dioxide evolved from the polymerization reaction leave. Small mistakes, either in the as submitted the amount of carbon dioxide found or the amount of primary or secondary alcohol, which is added to the reaction mixture in order to terminate the polymerization, lead either to free alcohol groups or free isocyanate groups in the resulting the product, which leads to instability during prolonged storage. Moreover, if unbalanced. Arylene diisocyanates, such as 2,4-toluene diisocyanate, are used in the process, it is found that the terminal Isocyanate groups predominantly adjacent to Methyl group, which the isocyanate group with further reactions sterically hindered

In contrast, the inventive method can be used to urethane-terminated polycarbodiimides of a reproducible structure and a produce wider molecular weight range than was done by the known methods. Besides that it is not necessary to monitor the evolution of carbon dioxide from the polymerization reaction, so that a major source of error is eliminated.

In addition, the reaction protects against the occurrence of free isocyanate groups or alcohol groups in the end product, creating storage problems be eliminated. The herge according to the method according to the invention presented product is in structure and properties significantly different from polycarbodiimides with urethane end groups made by known methods getting produced. These significant differences appear as a better shelf life of the product, improved action against hydrolytic degradation, improved heat stability, as the complete absence of isocyanate group peaks in the IR absorption spectra and as a significant difference in the Speed of reaction between this particular

6s product and those of the prior art recognized reaction participants, such as 2-ethyl-hexacarboxylic acid and acetic acid, in appearance. Ksuptsuigsbc of the vcr! Icgcr.dcn invention is therefore

to provide a process for the production of polycarbodiimides with urethane end groups that is easier is to be controlled and monitored and its urethane-terminated polycarbodiimide products are reproducible Have a molecular structure and a broader molecular weight range than was previously possible, and which has an improved shelf life, improved high temperature resistance and have improved antihydrolytic stabilizing properties. Task of Another invention is to provide a process for making urethane terminated polycarbodiimides in a wider and more controllable molecular weight range without the monitoring required heretofore of the carbon dioxide developed during the carbodiimide-forming reaction and without the possibility the appearance of free alcohol and isocyanate groups in the finished product. In addition, should According to the invention, urethane-terminated polycarbodiimides with a high proportion of hindered carbodiimide groups can be produced.

You can use a wide variety of arylene diisocyanates in which the Isocyanate groups of unequal reactivity, use including e.g. B.

Toluene-2,4-diisocyanate,

2-methylnaphthalene-1,5-diisocyanate, 3-methyl-4,4'-diisocyanatodiphenylmethane, S-ChloM / l'-diisocyanatodiphenylmethane, S-methoxy ^ / t'-diisocyanatodiphenylmethane, 2,4-diisocyanatochlorobenzene and cumene-2,4-diisocyanate.

Where one isocyanate group is noticeably more reactive than the other, as in the case of Toluo! -2,4-diisocyanate, where the isocyanate group in the 4-position is much more reactive than the isocyanate group in the 2-position, due to the absence of steric influences in the 4-position and the presence of steric Obstruction in the 2-position by the methyl group in the 1-position is the urethane end on the polycarbodiirtide essentially free from disabilities while the carbodiimide groups are relatively highly hindered. this is because the initial reaction with the aliphatic primary or secondary Alcohol with the more reactive groups, e.g. B. with the isocyanate group in the 4-position of the toluene-2,4-diisocyanate, takes place and then the polymerization to the carbodiimide structure via the in the disabled 2-position standing free isocyanate groups takes place This differs significantly from what occurs when the arylene diisocyanate first to

Carbodiimide is polymerized, since in this case the Polymerization takes place at the more reactive points, namely the isocyanate group in the 4-position, leaving the unreacted isocyanate group in the 2-position as that which passed through Implementation with the aliphatic alcohol should be completed. The resulting product is this special type of reaction would have urethane end groups in a sterically hindered position while ίο the carbodiimide groups are relatively unhindered and more reactive would be. Other arylene diisocyanates, their ! socyanate groups do not react immediately, close m-xylene-2,5-diisocyanate and 3,5-dimethylbiphenyl-4,4'-diisocyanate one.

Arylene diisocyanates with groups of the same reactivity can be mixed with arylene diisocyanates that are different reactive isocyanate groups, such as toluene-2,4-diisocyanate, are mixed to form a Customize a wide variety of carbodiimide reaction products. To examples of this Arylene diisocyanates with isocyanate groups of the same reactivity include toluene-2,6-diisocyanate, p-phenylene diisocyanate and 4,4'-diisocyanatodiphenyl methane (commonly known as "MDI"). Usable for others than arylene diisocyanate Starting materials include diisocyanate mixtures in which the reaction rate of the isocyanate groups of the various parts is significantly different, such as mixtures of 4,4'-diisocyanatodiphenylmethane with durol diisocyanate.

Examples of the primary and secondary aliphatic Alcohols are methyl alcohol, ethyl alcohol, isopropyl alcohol, sec-butyl alcohol, isoamyl alcohol, n-hexanol, cyclohexanol, 2-chloro-1-propanol, 2-octanol, Methylphenylcarbinol, benzyl alcohol, diethyl glycol mono-n-butyl ether and cinnamon alcohol. Preferably the alcohols contain no more than about 12 carbon atoms. Tertiary alcohols and phenols, Cresols, naphthols and other compounds in which the hydroxyl group is directly attached to the aromatic Ring bound are not suitable.

A stoichiometric excess alcohol, molar ratio OH: NCO = 1: 4 to 1:40, is used with the Arylene diisocyanate reacted so that not all isocyanate groups are converted into urethane groups. In this way, the molecular weight of the finished polycarbodiimide with urethanent groups can be controlled exactly and reproducibly. To calculate the theoretical molecular weight Mn the following theoretical structural formula is used

R-O-C-NH- (ArN = C = N-). —Ar —NH-C —O —R

wherein Ar is an aromatic group of Arylenendiisocya nates and R is an organic group of alcohol According to this formula, the molecular weight is therefore:

Mn = 2 (MG • ROH) + «(MG • ArNCN) + MG • Ar (NCO) ₂

For example, when ROH is methanol, Ar (NCO) _{2 is} toluene-2,4-diisocyanate, ArNCN is the following group :

NCN-

and π = 3, a theoretical molecular weight of 628 is obtained. The molecular weight can also be from the carbodiimide "NCN" content of the manufactured Product calculated according to the following formula will:

Mn = MG * ArNCN

2MG- ROH + MG • Ar (NCO) ₂

4000 % NCN

- MG ■ ArNCN + MG Ar (NCO) ₂ + 2MG RAW

So the molecular weight can be calculated in advance according to the above formula and then; on Accuracy can be checked by titrating the guanidine with standardized HCl, which is obtained by adding of ethylamine is formed into a sample of the produced Polycarbodiirnides. By this method There is no need to monitor the evolution of carbon dioxide, which occurs during the polymerization of the partially urethane-terminated arylene diisocyanate to polycarbodiimide takes place, one can rather develop it freely and thus eliminate potential errors that get into the end product due to errors in the monitoring of the carbon dioxide content, as is the case with the known procedure is the case

The solvent used in the usual way as a diluent in which the arylene diisocyanate in the stoichiometrically insufficient amount is reacted on primary or secondary aliphatic alcohol, must not contain any groups with Isocyanates or alcohols react under the polymerization conditions. In other words, that Solvents must not contain any active hydrogen atoms that react with the isocyanate groups would. In addition, the solvent should be the arylene diisocyanate, the aliphatic alcohol and the Easily dissolve the polymeric carbodiimide formed. Examples of suitable solvents therefor include Benzene, toluene, the xylenes, ethylbenzene, isopropylbenzene, mesitylene, cyclopentane, η-hexane, cyclohexane, n-heptane, methylcyclohexane, tetramethylethylene, diisobutylene, chlorobenzene, methylene chloride, ethylidene Chloride, chloroform, carbon tetrachloride, ethylene chloride, methylene bromide, o-dichlorobenzene, bis-chloromethyl ether, bis-isopropyl ether, dioxane, tetrahydrofuran and pyridine.

The reaction between the primary or secondary aliphatic alcohol and the Arylendiisocyanat is exothermic, and it is considered generally right, not to allow the reactive mixture to rise higher than about 5O to ⁰ C by the heat generation. In the presence of large amounts of solvent, the solution may need to be heated to reach this temperature. When the reaction between the two parts is complete, the mixture is cooled to near room temperature and a polycarbodiimide-forming catalyst is added in order to convert the partially urethane-terminated arylene diisocyanate through the reaction between the free isocyanate groups, namely those that remain in the reaction between the alcohol and the arylene diisocyanate polymerize a polycarbodiimide with urethane end groups.

Carbodiimide-forming catalysts include phospholines, phospholine oxides, and sulfides. The phospholine oxides and sulfides are in US patents No. 26 63 737 and 26 63 738. The phospholi- <-5 Dinoxides are described in U.S. Patent No. 2,663,739. The corresponding phospholines and Phospholidine can be replaced by a lithium aluminum hy reduction of the corresponding dichlorophospholine or phospholidine can be produced. These dichloro compounds are also used for the production of the The aforementioned oxides and sulfides are used and are described in US Pat. No. 2,663,736. Representative examples of suitable catalysts are 1-ethyl-3-phospholine, 1-ethyl-S-methylO-phospholine-1-oxide, 1-ethyl-S-methyl-S-phospholine-1-sulfide, l-ethyl-3-methyl-phospholidine and l-ethyl-3-methyl-phospholidine-i-oxide. The preferred catalyst is l-PhenylO-methyl-S-phospholine-1-oxide. The specific amount of catalyst used is largely dependent on the reactivity of the catalyst itself and the arylene diisocyanates used. A concentration range of 0.1-10 parts by weight of catalyst per 100 parts by weight of arylene diisocyanate is suitable. About 0.5-1.0 parts of the preferred catalyst are satisfactory when using diisocyanates such as toluene diisocyanate, are polymerized.

Either during or after the polymerization of the arylene diisocyanate to give the polycarbodiimide, in usually fillers and other finely divided particulate materials for the reaction mixture be given to dilute the formed polycarbodiimide and a practical and useful one provide sustaining diluent for the final product. About these particulate fillers can include carbon black, clay, silica, talc, zinc and magnesium oxides, calcium and magnesium carbonate, titanium dioxide and Plasticizers include. The polycarbonamides produced according to the invention are usually solids, their physical properties largely depend on the special one used in the implementation Arylene diisocyanate or arylene diisocyanate mixture and the ratio of alcohol to isocyanate depend. Infrared spectra of the polycarbodiimides with urethane end groups show a single NCN peak at 2130cm- ', a clear indication that free isocyanate groups are completely absent in the final product.

The following examples are intended to implement the illustrate without, however, limiting the present invention. Unless otherwise stated all parts are parts by weight and all percentages are percentages by weight.

example 1

A polycarbodiimide with urethane end groups is prepared according to the invention as follows: One gives 1000 ml of dry toluene in a cleaned and dried reaction vessel and puts it under dry nitrogen. 290 g of a mixture of 2,4- and 2,6-toluene diisocyanate isomers are added in one Ratio of 4: 1 to the toluene in the reaction vessel and stir the mixture. 26.66 g of dry methyl alcohol are added dropwise under nitrogen stirred toluene diisocyanate mixture in toluene, whereby the jacket of the reaction vessel is cooled, so that the heat dissipation of the reaction does not affect the mixture warmed to a temperature higher than 50 "C. Stirring is continued and the

Reaction temperature / white hours at 40 -45 ^C C. The Kcaktionsnubchuiif: is then cooled to room temperature, and there will be 1.333 g l-Phcnyl-3-mcthyl-3-phospholine-l-oxide added. The reaction mixture is slowly warmed while a stream of dry nitrogen is bubbled through it. The course of the reaction is monitored using the IR absorption spectra of the solution between 2000 and 2500 cm '. The N - C = O peak at 2270 cm 'disappears while the N = C = N peak appears at 2130 cm' and finally the only absorption pack remains in this region. One can therefore see how the

Table I.

Isocyanate groups begin to disappear and the carbodiimide groups to appear in their place begin to show that once the N = C = O peak at 2270 cm- 'has disappeared, the product is none contains more free isocyanate groups.

The procedure is repeated using different alcohols and different amounts of Alcohol and toluene diisocyanate to produce polycarbodiimides of varying NCN / urethane ratios and varying To produce molecular weights. These repeated experiments and their results are in Table I below compiled.

alcohol TDI *) / RAW O Theor. VPO ") Theor. Actually (RAW) Mol.-Ver Il Moi.-Gcw. determination % NCN % NCN ratio, NCN / HNCOR MG. Loading ratio kung in the product 2-ethylhexanol 2 1.5 824 680 14.6 14.1 Methanol 2 1.5 626 570 19.1 19.6 Methanol 2 1.5 626 520 19.1 18.8 Methanol 4th 3.5 1148 1290 24.4 24.6 Methanol 8th 7.5 2188 1670 27.5 27.6

*) TDI > = toluene diisocyanate.
**) = vapor phase osmomelry.

This example shows some of the parameters that can be varied using polycarbodiimides Manufacture urethane end groups of various molecular weights and structures.

Example 2

Two samples are made using the same materials in the same quantities as in the The first two approaches in Table I can be used, but that of US Pat. No. 2,941,983 applies the procedure described. The products are left in a benzene solution and preserved For a while to observe their stability. The samples and the findings about their storability are summarized in Table II below.

Table II

Manufacturing

alcohol

Observations during storage *)

According to example 1
U.S. Patent 29 41 983
According to example 1
U.S. Patent 29 41 983

2-ethylhexanol liquid, slightly cloudy solution

2-ethylhexanol yellow gelled solid

Methanol liquid, slightly cloudy solution

Methanol heavy white precipitate formed after 2 days

*) Stored for four weeks at room temperature in sealed glass bottles.

This example demonstrates the superior shelf life of using the method of the present invention Polycarbodiimides prepared with urethane end groups compared to the same by known processes manufactured products.

55 Example 3

The procedure described in Example 1 is repeated and the 26.66 g of dry methanol become replaced by an equal molar amount of 2-ethylhexanol. Samples of the corresponding polycarbodiimide of Example 1 and the corresponding material based on 2-ethylhexanol are in one Procedure that is not protected here. separated with 0.25 n-2-ethylhexanecarboxylic acids in benzene implemented. Samples of like polycarbodiimides are made using those described in the US patent 29 41 983 and puts these products into one another at the same concentration Benzene solution with 0.25 n-2-ÄthyIhexancarbonsäure to the prepared by the process according to the invention Polycarbodiimides react much more slowly; than those known by the patented traverser Hergestallten suggesting significant differences in the structures or in the position of the attached Groups on the polycarbodiimides

Similar results are obtained when that much various polycarbodiimides reacted with acetic acid at the same concentration in a benzene solution will.

This example also shows the major differences in the molecular structure after this one urethane-terminated polycarbodiimides made by both processes.

From samples of the Materia lien produced in Example 3, the benzene is stripped in a vacuum, and the solid products are extracted. Then mar

a conventional differential therino analysis (DTA) and thermal analysis (TGA). Although differential thermal analysis does not show any major endothermic or exothermic process in any of the Products shows, the thermogravinielrische analysis reveals that the products produced by the process according to the invention are thermally more stable than the products manufactured using state-of-the-art processes. Values of the conventional thermogravimetric analysis tests (TGA) are shown in Table IV below.

Table IV

proceedings temperature 600 ⁰ C at 10% Weight Weight loss loss

Present invention 275 ° C 30%

US Patent 29 41983 244 ° C 36%

This example shows that the structure of the polycarbodiimide with urethane end groups produced by the process according to the invention differs significantly from that of the product produced by the known process, since the conventional TGA tests reveal that the product produced by the process according to the invention has a lower weight loss of 600 ⁰ C and a higher decomposition temperature than the corresponding product of the prior art.

10

Proof of technical progress Application example 1

A conventional peroxidizable polyester polyurethane resin compound is prepared according to the formulation shown in Table V (A) below. The formulation is ground until all ingredients are evenly dispersed throughout the rubber phase. The mixture is divided into three servings. A first portion (sample A) is used without any further addition. Four parts of an industrial polycarbodiimide per 100 parts of polyester urethane are added to a second portion (sample B). Four parts per 100 parts of urethane of a urethane-terminated polycarbodiimide with a molecular weight of about 600, prepared according to the process of the invention using methanol and the toluene diisocyanate used in Example 1, are added to a third portion (sample C). The three samples are ground, and flat tensile strength samples are cut from the plates and ^{cured in the press at 160 °} C. for 20 minutes. Determining the initial properties and the properties after 24stiindigem aging in a forced air oven at 149 ⁰ C the results are shown below in Table V (B).

Table V (A)

Components

Part?

Technical, grindable polyester urethane 100 FEF carbon black 25

40% dicumyl peroxide on calcium carbonate 4.5

Table V (B)

properties Sample A Sample B Sample C Original 300% module, kg / cm * 148 130 138.7 Tensile strength, kg / cm ² 324.7 302 292 Strain, % 560 560 560 Hardness, Shore A 60 60 60 Aged in air for 24 hours at 149 ° C 300% module, kg / cm * 73.8 66.8 120 Tensile strength, kg / cm ² 225 207 193 Strain, % 710 770 470 Hardness, Shore A 56 59 62

This example clearly demonstrates the improvement in heat stabilization imparted by peroxide cured polyester urethane rubbers using the urethane terminated polycarbodiimides of the present invention is compared to the products manufactured by known processes. Note that the original 300% modulus values for all three samples in are roughly the same, after 24 hours of aging at 149 ° C in air, the 300% modulus for sample A is the contains no polycarbodiimide, reduced by 50%, for Sample B, which contains an industrial polycarbodiimide produced by known processes, is still further reduced, but in sample C, which contains the polycarbodiimide prepared according to the invention with urethane end groups, it is only slightly compared to his original value decreased

Application example 2

Another conventional peroxy-curable polyester urethane rubber compound is used according to the formulation given in Table VI (A) below The formulation is ground until all ingredients are uniform throughout the rubber pha se are dispersed. The mixture is made in three servings divided A first portion (sample D) is used without any further additives. For a second portion (sample E) four parts of an industrial polycarbodiimide stabilizer are added per 100 parts of polyester urethane. to a third portion (sample F) is added with four parts per 100 parts of urethane of a polycarbodiimide Urethane end groups obtained by the process of the invention using methanol and the in

Example I used toluene diisocyanate prepared has been. The three samples are ground and the plates become flat tensile strength samples cut and cured in the press for 20 minutes at 160 ° C. You determine the original properties and the properties after aging for 70 hours in water at 93.3 "C, the results are in Table VI (B) summarized below.

Table Vl (Λ)

Components

Technical, grindable polyester urethane 100

SAF RuO 25

40% dicumyl hydroxide on calcium carbonal

Stearic acid, lubricant for grinding 0.2

Table VI (B)

properties Sample D Sample E. Sample F. Original 300% modulus, kg / cm- ' 137 130.9 133 Tensile strength, kg / cm ² 169.2 410.7 414 Strain, % 580 560 570 Hardness, Shore A 63 66 67 Aged for 70 hours in water at 93.3 ° C 300% module, kg / cm * 3.52 66.8 93.2 Tensile strength, kg / cm ² 19.3 282.7 251.7 Strain, % 1220 640 550 Hardness, Shore A 26th 60 65

This example clearly shows the improvement of the pen bestowed over the known ones

hydrolytic stability, the peroxide-cured poly process manufactured products. By far the

Ester urethane rubbers when using the best in the present invention retain their overall properties, in particular

The polycarbodiimide according to the invention with urethane end group 300% modulus in sample F was obtained.

Claims (1)

Claim: Process for the preparation of polycarbodiimides with terminal urethane groups by reacting arylene diisocyanates in which the isocyanate groups are of unequal reactivity, optionally with the concomitant use of arylene diisocyanates with isocyanate groups having the same reactivity as carbodiimide-forming catalysts and a stoichiometric deficit of alcohols from the group of the primary and secondary aliphatic alcohols, characterized in that a) the above arylene diisocyanates, with a stoichiometric deficit in the ratio of alcoholic hydroxyl groups Isocyanate groups in the range from 1: 4 to 1:40 of the alcohols from the group of primary and secondary aliphatic alcohols are reacted, so that not all isocyanate groups in Urethane groups are converted, and b) carbodiimide-forming catalysts are mixed in and the partially urethane-terminated Arylene diisocyanates polymerized to polycarbodiimides with terminal urethane groups will.