US3092594A - Polyurethane resin obtained from coal tar pitch reaction products and process for preparing same - Google Patents

Description

ilnired f tates This invention relates to the production of plastic materials. More particularly, this invention is concerned with improvements in the use of coal tar pitch and products obtained therefrom.

The term coal tar pitc as used herein is understood in the tar industry to designate a residue of coal tar distillation which is substantially insoluble in alkali, ethanol and isopropanol. The term is used in this sense in the following specification and in the claims. The term is further defined in Encyclopedia of Chemical Technology, vol. 13, page 625, published by The In-terscience Encyclopedia, Inc., New York, New York, 1954, and in Asphalts and Allied Substances, Fifth Edition, Vol. 1, page 59, published by Van Nest-rand, 1945 It has been proposed heretofore to prepare coatings from coal tar pitch; indeed even moldings have been prepared. The coatings are conventionally used for coating pipelines and roofing, for example. Two methods of applying these coatings are, generally used, namely, hot applied coatings and cold applied coatings. Neither method is entirely satisfactory. The hot applied coatings involve the use of a heating kettle and attendant crews. The cold applied coatings are unsatisfactory because they are slow to dry and yield only soft coatings. Where moldings have been prepared, they are very fragile and indeed this property makes them useful in the production of clay pigeons which are used as targets for trap shooting and skeet shooting. Molded clay pigeons are prepared by heating coal tar pitch with limestone dust and casting the mixture in a mold. The resulting clay pigeons are so fragile that they have no other utility. It has not been possible heretofore to use coal tar pitch in the production of more refined plastics such as foam and nonporous elastomeric products.

It is, therefore, an object of this invention to provide improved plastics which are based on coal tar pitch. Another object of this invention is to provide improved coal tar pitch coatings. A further object of the invention is to provide improved coal tar pitch moldings. Still another object of the invention is to provide cellular plastics based on coal tar pitch; Another object of the invention is to provide nonporous plastics based on coal tar pitch. A particular object of the invention is to provide coal tar pitch coatings which have improved hardness and resistance to organic solvents.

The foregoing objects and others which will become apparent from the following description are accomplished in accordance with the invention, generally speaking, by providing plastics obtained from an organic polyisocyanate and the reaction product of coal tar pitch and an alkylene oxide or alkylene carbonate. In accordance with the invention, therefore, cellular and noncellular plastics are produced by reacting coal tar pitch in a first step with an alkylene oxide or alkylene carbonate and then combining the resulting product with an organic polyisocyanate in a second step to produce the desired type of plastic. The exact nature of the reaction mechanism leading to the production of these plastics is not completely understood. However, it is believed that the alkylene oxide or alkylene carbonate reacts with reactive groups in the coal tar pitch including aliphatic hydroxyl harem ice 2 groups, carboxylic acid groups, phenolic hydroxyl groups and/ or amino groups to produce side chains containing terminal hydroxyl groups which will in turn react with an organic polyisocyanate to produce a polyurethane plastic.

Any suitable coal tar pitch may be used to prepare the plastics of the invention. Coal tar pitch is a complex mixture of polynuclear aromatic compounds containing phenolic groups, amino groups and other active hydrogen containing groups. The consistency of coal tar pitch may vary from that of heavy tar to that of hard pitch or semicoke. The coal tar pitch preferably has a softening point of from about F. to about 300 F. The softening points referred to are determined by the ASTM standard ring and ball method D36-26 unless otherwise specified and penetration values referred to herein are determined by ASTM method D5-52. The coal tar pitch will react readily with an alkylene oxide or alkylene carbonate. The products of the reaction between the alkylene oxide and/or alkylene carbonate are hereinafter referred to as modified coal tar pitch.

Any suitable alkylene oxide and/or alkylene carbonate may be used to modify the coal tar pitch. It is preferred that the alkylene oxides contain only one epoxy group and the use of cyclic carbonates is preferred. Therefore, suitable alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, amylene oxide, styrene oxide, butadiene diepoxide, epichlorohydrin and the like. Suitable alkylene carbonates are, vfor example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 1,2-glycerine carbonate and the like. The reaction of the coal tar pitch with the alkylene oxide and/or alkylene carbonate is carried out in a straight-forward and convenient manner by simply melting the coal tar pitch and mixing it with the alkylene oxide or alkylene carbonate. The resulting mixture is then heated until the two components have become combined. Preferably, a chemical combination as set forth above is efiected during this heating stage. Where alkylene carbonates are employed the reaction will be essentially complete when gas evolution ceases. The resulting product has a much lower isocy-anate equivalent than the unmodified coal tar pitch. Isocyanate equivalent is the amount of the coal tar pitch or modified coal tar pitch in grams which will react with one mol of phenyl isocya-nate. The change in the isocyanate equivalent of the coal tar pitch after it has been modified with an alkylene oxide or alkylene carbonate shows that there are very few reactive groups in the unmodified material.

The modified coal tar pitch may be reacted with any suitable organic polyisocyanate to produce either cellular or noncellular plastics as more particularly set forth below.

Suitable organic polyisocyanates include aromatic, aliphatic and heterocyclic polyisocyanates. In other words, any suitable organic radical may be bonded to a plurality of isocyanate groups to form the organic polyisocyanate used in the process of the present invention including acyclic, alicyclic, aromatic and heterocyclic radicals. Suitable organic polyisocyanates, are, therefore, ethylene diisocyanate, ethylidene diisocyanate, propylene 1,2 diisocyanate, cyclohexylene 1,2 diisocyanate, m-phenylene diisocyanate, 2,4-toluylene diisocyanate, 2,6 toluylene diisocyanate, 3,3 dimethyl-4,4'-bi, phenylene diisocyanate, 3,3'-dimethoxy-4,4T-biphenylene diisocyanate, 3,3'-diphenyl-4,4'-biphenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4-biphenylene diisocyanate, p,p',p"-triphenylmethane triisocyanate, 1,5-naphthalene diisocyanate, furfurylidene diisocyanate or polyisocyanates in a blocked or inactive form such as the bis-phenyl carbamates of 2,4- or 2,6-toluylene diisocyanate, p,p-diphenylrnethane diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate and the like. It is preferred to use the commercially available mixture of toluylene diisocyanates which contains 80 percent 2,4-toluylene diisocyanate and 20 percent 2,6-toluylene diisocyanate or 4,4-diphenylmethane diisocyanate.

Itis sometimes desirable to mix the modified coal tar pitch with other organic compounds containing at least two active hydrogen containing groups as determined by the Zerewitinofi method. Suitable organic compounds containing active hydrogen containing groups are, for example, hydroxyl polyesters, polyhydric polyalkylene ethers, polyhydric polythioethers and the like. These compounds preferably have a molecular weight between about 500 and about 10,000, most preferably between about 1,000 and about 5,000, hydroxyl numbers of about 25 to about 600 and acid numbers Where applicable below about 5. -Any suitable hydroxyl polyester may be used such as are obtained, for example, from polycarboxylic acids and polyhydric alcohols. Any suitable polycarboxylic acid may be used such as, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassylic acid, thapsic acid, maleic acid, fumaric acid, glutaconic acid, m-hydromuconic acid, 5- hydromuconic acid, u-butyl-a-ethyl-glutaric acid, cc-B-diethylsuccinic acid, isophthalic acid, terephthalic acid, hemilellitic acid, trimellitic acid, trimesic acid, mellophanic acid, prehnitic acid, pyromellitic acid, benzenepentacarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 3,4,9,l-perylenetetracarboxylic acid and the like. Any suitable polyhydric alcohol may be used such as, for example, ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2- butylene glycol, 1,5-pentane diol, 1,4-pentane diol, 1,3 pentane diol, 1,6-hexane diol, 1,7-heptane diol, glycerine, trimethylol propane, 1,3,6-hexanetriol, triethanolamine, pentaerythritol, sorbitol and the like.

Any suitable polyhydric polyalkylene ether may be used such as, for example, the condensation product of an alkylene oxide or of an alkylene oxide wtih a polyhydric alcohol. Any suitable polyhydric alcohol may be used such as those disclosed above for use in the preparation of the hydroxyl polyesters. Any suitable alkylene oxide may be used such as, for example, ethylene oxide, propylene oxide, butylene oxide, amylene oxide and the like. Of course, the polyhydric polyalkylene ethers can be prepared from other starting materials such as, for example, tetrahydrofuran, epihalohydrins such as, for example, epichlorohydrin and the like as well as aralkylene oxides such as, for example, styrene oxide and the like. The polyhydric polyalkylene ethers may haveeither primary or secondary hydroxyl groups and preferably are polyhydric polyalkylene ethers prepared from alkylene oxides having from two to five carbon atoms such as, for example, polyethylene ether glycols, polybutylene ether glycols and the like. It is often advantageous to employ some trihydric or higher polyhydric alcohol in the preparation of the polyhydric polyalkylene ethers so that some branching exists in the product. Generally speaking, it is advantageous to condense from about 5 to about 30 mols of alkylene oxide per functional group of the trihydric or higher polyhydric alcohol. The polyhydric polyalkylene ethers may be prepared by any known process such as for example, the process disclosed by Wurtz in 1859 and in Encyclopedia of Chemical Technology, vol. 7, pp. 257-262, published by Interscience Publishers Inc. (1951) or in US. Patent 1,922,459.

Any suitable polyhydric polythioether may be used .uchj as, for example, the condensation product of thioiglycol or the reaction product of a polyhydric alcohol uc h' as. is disclosed above for the preparation of the byx lpolyesters With any other suitable thioether glycol.

Other suitable polyhydric polythioethers are disclosed in US. Patents 2,862,972 and 2,900,368.

The hydroxyl polyester may also be a polyester amide such as is obtained, for example, by including some amine or amino alcohol in the reactants for the preparation of the polyesters. Thus, polyester amides may be obtained by condensing an amino alcohol such as ethanolamine with the polycarboxylic acids set forth above or they may be made using the same components that make up the hydroxyl polyester with only a portion of the components being a diamine such as ethylene diamine and the like.

In accordance with a preferred embodiment of the invention coatings are prepared by mixing the modified coal tar pitch with an organic polyisocyanate or blocked polyisocyanate such as, for example, the reaction product of 2 mols of pentanol with 1 mol of a toluylene diisocya-. nate, such as 2,4-toluylene diisocyanate, and applied to any suitable substrate. The coating solutions are pref erably prepared in an inert organic solvent such as, for example, xylene, ethyl acetate, ethylene glycol monoethyl ether acetate and the like. Moreover, the coating compositions can be applied by any suitable method such as, for example, brushing, dipping, spraying and the like. The coating compositions are preferably applied in the above-defined inert organic solvent. Where the blocked isocyanates are used, it is necessary to heat the coating composition to release the isocyanate. For this purpose temperatures above about 300 F. are usu-. ally sufiicient. The coatings obtained, however, will air dry if they are mixed with an organic polyisocyanate in a solvent and applied directly to a substrate such as metal, for example, steel, wood and the like. Moreover, the coatings obtained are hard and resistant to organic solvents while retaining the water repellency character-. istic of coal tar coatings. The coatings of the invention are particularly useful for coating pipelines and for roofing and the like.

It is also possible in accordance with the invention to prepare cellular plastics. In accordance with this process the modified coal tar pitch is mixed with an organic poly-' isocyanate and water or a halohydrocarbon such as trichlorofluoromethane, dichlorodifluoromethane and the like and allowed to react to produce, a cellular plastic. The cellular plastics of the invention are preferably prepared by combining the modified coal tar pitch with an organic polyisocyanate and water in the presence of a catalyst and a foam stabilizing agent. Any suitable catalyst may be used including, for example, tertiary amines such as, for example, triethylene diamine, N-methyl morpholine, N-ethyl morpholine, diethyl ethanolamine, N- coco morpholine, l-methyl-4-dimethyl amino ethyl piperazine, 3-methoxy-N-dimethyl propyl amine, N-dimethyl- N-methyl isopropyl propylene diamine, N,N-diethyl-3- diethyl amino propyl amine, dimethyl benzyl amine and the like. Other suitable catalysts are for example, tin compounds such as, stannous chloride,tin salts of carboxylic acids, such as dibutyl tin di-Z-ethyl hexoate as well as other organo metallic compounds such as are disclosed in US. Patent 2,846,408 and in copending application S.N. 835,450.

Suitable foam stabilizers are for example, polydimethyl siloxanes or alkyl silane oxyalkylene block copolymers. The latter type of silicone oil is disclosed in US Patent 2,834,748. Where polyhydric polyalkylene ethers are included in the reaction mixture to prepare a cellular polyurethane plastic, it is preferred to employ the silicone oil of the above patent which has the formula wherein R, R and R" are alkyl radicals having 1 to 4 carbon atoms; p, q and r each have a value of from 4 to 8 and (C H O) is a mixed polyoxyethylene oxypropylene group containing from 15 to 19 oxyethylene units and from 11 to 15 oxypropylene units with z equal to from about 26 to about 34. Most preferred is a compound having the formula wherein (C H O) is a mixed polyoxyethylene and oxypropylene block copolymer containing about 17 oxyethylene units and about 13 oxypropylene units.

The cellular plastics of the invention may be used to prepare improved sound absorbing coatings on metal, for example. Thus, they are particularly useful in the preparation of undercoatings for automobiles and the like.

It is also possible to prepare nonporous plastics from the modified coal tar pitch. The reaction leading to the production of the hard nonporous plastics is usually an exothermic reaction and the reaction product will gel in a short time to yield a hard plastic. In accordance with this process, the modified coal tar pitch is mixed with an organic polyisocyanate and cast in any suitable mold. The castings are useful as sealants and the like and are resistant to organic solvents in contrast to the unmodified coal tar pitch.

The invention is further illustrated by the following examples in which the parts are by weight unless otherwise indicated.

EXAMPLE 1 (a) About 200 grams of a coal tar pitch which is insoluble in alkali, ethanol and isopropanol and has an isocyanate equivalent of about 16,300 is combined with about 40 grmns of ethylene carbonate and heated to about 200-220 C. After about 30 minutes gas evolution begins. and continues for about 45 minutes when it essentially ceases. The reaction flask has lost a weight of about 23 grams; the theoretical weight loss of CO is about 20 grams. A black liquid is obtained which is less viscous than the starting material. The isocyanate equivalent of the product is about 693.

(b) Example 1(a) is repeated except about 80 grams of ethylene carbonate is used. The gas evolution begins after about 30 minutes heating and continues for about 90 minutes. The weight loss is about 44 grams; the theoretical loss of CO is about 40 grams. This material is less viscous than that obtained in Example 1(a). The isocyanate equivalent of the product is about 617.

(0) About 260 parts of the modified coal tar pitch as prepared in Example 1(a) is combined with about 260 parts xylene and about 350 parts of the reaction product of about 1 mol l,'3-butane diol, about 1.5 mols trimethylol propane and about 6.2 mols of a mixture of 80 percent 2,4- and 20 percent 2,6-toluylene diisocyanate in a 75 percent by weight solids solution in ethyl acetate. The resulting solution is applied to a steel panel with a doctor blade and allowed to air dry for about three days. A hard coating is obtained on the steel panel which is resistant to aromatic solvents such as toluene and will now flow at temperatures below about 350 F.

(d) Example l-(c) is repeated except the coating is baked at a tem erature of about 300 F. for about 30 minutes. Similar results are obtained.

(e) Example 1(c) is repeated except the modified coal tar pitch prepared as in Example 1(b) is used. A hard coating is obtained on the steel panel which air dries in less than three days. The resulting coating is highly resistant to aromatic solvents.

EXAMPLE 2 (a) The coal tar pitches shown below in Table I are reacted with about 40 parts of ethylene carbonate per 100 parts of coal tar pitch, following the procedure of Example 1(a) except the total reaction time is about 7 hours and the temperature varies between about 170 C. and about 190 C.

Table 1 Coal Tar Pitch Physical Properties RT-2 RT-6 RT-9 RT-12 Engler specific viscosity at 104 F. (40 0.).... 8-13 Engler specific viscosity at 122 F. (50 C. 25-40 Float test at 89.6 F. (32 0.)

S cond 120-300 Float test at 122 F. (50 C.)

Seconds 150 220 Distillation of water free material:

Total distillate, percent by weight Start to338 F. (170 0.)- 0.0 7.0 0.0-5.0 0.0-1.0 0.0-1.0 Start to 518 F. (270 0.)

Maximum 35. 0 25. 0 15. 0 10.0 Start to 572 F. (300 C.) Maximum 45.0 35.0 25.0 20.0 Residue, fusing-point, F -149 95-158 95-158 104-158 Soluble in carbon disulfide, percent (Minimum) 88 83 78 75 Water, percent by yo me,

Maximum 2. 0 1. 5 0.0 0.0

The products are black liquids which are further reacted as indicated below.

(b) About 250 parts of each of the modified coal tar pitches prepared as described in Example 1(a) are combined with about 350 parts of the reaction product of 1,4-butane diol, triethanol propane and the mixture of toluylene diisocyanates employed in Example 1(b) and 250 parts of xylene. Each of these solutions is then coated onto a steel panel and air dried for about three days. A hard coating is obtained which is resistant to organic solvents such as toluene.

(0) About parts of the RT-2 ethylene carbonate condensation product prepared in Example 2(a) are cornbined with about 30.5 parts of a mixture of 80 percent 2,4- and 20 percent 2,6-toluylene diisocyanate. An exothermic reaction occurs immediately and the mixture gels within about one hour to yield a hard elastomeric plastic.

(d) About 100 parts of the RT-9 ethylene carbonate condensation product prepared in Example 2(a) are combined with about parts of the polyisocyanate employed in Example 2(b) and heated to about 70 C. The mixture gels in about 5 minutes to yield a hard elastomeric plastic.

(e) About 50 parts of the RT-9 ethylene carbonate condensation product prepared in Example 2(a), about 50 parts of a trihydn'c polyalkylene ether triol obtained from condensation of propylene oxide and glycerine to a molecular weight of about 3,000 and having a hydroxyl number of about 56 are mixed and then combined with about 20 parts of a mixture of 80 percent 2,4- and 20 percent 2,6-toluylene diisocyanate. about 20 parts of trichlorofiuoromethane, about 0.1 part of stannous octoate, about 0.6 part of N,N,N',N'-1,3-butane diamine and about 1.5 parts of an alkyl silaue oxyalkylene block copolymer having the formula wherein (C H O) represents about 17 oxyethylene units and about 13 oxypropylene units in a machine mixer as disclosed in US. Reissue Patent 24,514. A soft black cellular polyurethane plastic is obtained which has a density of about 2.0 pounds per cubic foot and is suitable for use as a sound absorbing system for sheet metal and the like.

EXAMPLE 3 About 2,000 grams of the RT-9 shown in Table I are heated until molten in a 12 liter stainless steel resin reactor equipped with bafiies, a stirrer, a thermometer, a

vent and an addition line. Then about grams of powdered KOH are added and the reaction mixture is heated to about 160 C. About 400 grams of propylene oxide are then added overa period of about 30 hours while maintaining the pressure in the reactor below about p.s.i.g. The temperature of the reaction mixture is maintained between about 160 C. and 170 C. throughout the addition. After all the propylene oxide has been added, the heating is stopped and the reaction mixture is allowed to cool to about 100 C. ture is purged with HCl to neutralize the catalyst and finally with nitrogen to remove the HCl. On cooling, a liquid product is obtained which has an isocyanate equivalent of about 550. v I

(b) About 250 parts of the RT-9 propylene oxide condensation product prepared as described in Example 3(a) are combined with about 350 parts of the polyisocyanate employed in Example 2( b) in about 250 parts of xylene. The solution is applied to a steel panel with a doctor blade and allowed to air dry for about 3 days. A hard coating is obtained which is resistant to organic solvents such as toluene. Similar results are obtained by baking the coating for about 30 minutes at about 250 F.

It is to be understood that any other suitable coal tar pitch, alkylene oxide or carbonate, organic polyisocyanate, catalyst, stabilizer and the like could have been used in the foregoing examples in accordance with the preceding disclosure.

Although the invention has been described in considerable detail in the foregoing, it is to be understood that such detail is solely for the purpose of illustration and that many variations can be made by those skilled in the art without departing from the spirit and scope of the invention except as set forth in the claims.

What is claimed is:

1. Plastics obtained by a process which comprises reacting an organic polyisocyanate with the reaction product of a coal tar pitch and a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate.

2. Cellular plastics obtained by a process which comprises reacting an organic polyisocyanate with the reaction product of coal tar pitch and a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate in the presence of a blowing agent.

3. A coating composition obtained by a process which comprises reacting an organic polyisocyanate with the reaction product of coal tar pitch and a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate in an inert organic solvent therefor.

4. A substantially nonporous plastic obtained by a process which comprises reacting an organic polyisocyanate with the reaction product of coal tar pitch and a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate.

5. A process for the preparation of plastics which comprises reacting coal tar pitch with a. member selected from Then the reaction mix-' the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate in a first step and thereafter reacting the resulting product with an organic polyisocyanate.

6. A process for the preparation of a cellular plastic which comprises reacting an organic polyisocyanate with water and the reaction product of coal tar pitch and a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate.

7. A method for coating substrates which comprises mixing the reaction product of coal tar pitch and a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate with an organic polyisocyanate in an inert organic solvent therefor and applying the resulting solution to said substrate.

8. A process for the preparation of a substantially nonporous plastic which comprises mixing the reaction product of coal tar pitch and a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate with an organic polyisocyanate and casting the resulting mixture in a mold.

9. Polyurethane plastics obtained by a process which comprises reacting an organic polyisocyanate with a mixture of an organic compound containing at least two active hydrogen containing groups as determined by the Zerewitinofl: method and having a molecular weight of at least about 500 and the reaction product of coal tar pitch with a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate.

.10. In the preparation of coal tar coatings the improvement whichcomprises reacting coal tar pitch with a member selected from the group consisting of an alkylene oxide having 2 to 8 carbon atoms and an alkylene carbonate and thereeafter reacting the resulting product with an organic polyisocyanate.

. 11. A composition prepared by a process which comprises reacting an organic polyisocyanate with the product prepared by a proces which comprises reacting an alkylene oxide having 2 to 8 carbon atoms with a coal tar pitch.

12. The composition of claim 11 wherein said alkylene oxide is propylene oxide.

13. The composition of claim 11 where the reaction between said coal tar pitch and said alkylene oxide is car ried out in the presence of a catalyst.

14. The composition of claim 13 wherein said catalyst is KOH.

15. The composition of claim 11 wherein said alkylene oxide has only one epoxy group.

16. The composition of claim 11 wherein said alkylene oxide is ethylene oxide.

17. The composition of claim 11 wherein said organic polyisocyanate is a toluylene diisocyanate.

References Cited in the file of this patent UNITED STATES PATENTS 2,976,256 Whittier et a1. Mar. 21, 1961

Claims (1)

1. PLASTICS OBTAINED BY A PROCESS WHICH COMPRISES REACTING AN ORGANIC POLYISOCYANATE WITH THE REACTION PRODUCT OF A COAL TAR PITCH AND A MEMBER SELECTED FROM THE GROUP CONSISTING OF AN ALKYLENE OXIDE HAVING 2 TO 8 CARBON ATOMS AND AN ALKYLENE CARBONATE.