NL1013155C2 - Method for devulcanizing a rubber. - Google Patents

Description

- 1 - 5 PROCESS FOR DEVILLATING A RUBBER.

The invention relates to a process for devulcanizing a rubber, which rubber is obtained by vulcanizing a copolymer containing ethylene monomer units, monomer units of an α-olefin and monomer units of a polyunsaturated compound using a sulfur-containing compound. by heating the rubber at such a high temperature that devulcanization occurs and a product to be reused is obtained.

Such a method is known from the IRC '98 Conference Proceedings, Societé de Chimie 20 Industrielle, Paris, 12th-14th May 1998, p. 289-290.

This describes the devulcanization of a sulfur-containing vulcanized rubber containing ethylidene norbornene (ENB) as a polyunsaturated compound and where devulcanization takes place only after the sulfur-containing vulcanized rubber is heated over a long period of time and a devulcanizing agent has been added to the rubber.

A drawback of the known method is that the devulcanization is incomplete and moreover only takes place after long heating times at high temperatures and at high concentrations of a devulcanizing agent, so that the process is unfavorable.

1013155 - 2 -

The product obtained is therefore not easy to reuse.

The object of the present invention is to provide a method for devulcanizing a rubber in which a more complete devulcanization takes place in a simpler manner and with a shorter heating time.

This object is achieved by using the method which is characterized in that a rubber is obtained which is obtained by vulcanizing a copolymer containing monomer units of a polyunsaturated compound of the formula XR ° (I) wherein X is a by means of a coordination catalyst is polymerizable group with 2-20 C atoms and R ° is a chain with 2-30 C atoms containing at least one carbon-carbon double bond, wherein none of the C atoms of the double bond is part of a ring structure.

A further advantage is that it is possible to use lower concentrations of a devulcanizing agent in devulcanizing the rubber.

It is even possible to obtain complete or substantially complete devulcanization of the rubber without the addition of a devulcanizing agent.

The method according to the invention can take place with the equipment for processing polymers known in the literature.

i 0! o; ^ ^ * - 3 -

Examples of suitable devices are a press, an oven, a kneader, a stirred vessel, an autoclave or an extruder. Preferably an extruder or a kneader is used.

The heating during the process of this invention is carried out, for example, at a temperature of 50-400 ° C, preferably at a temperature of 150-350 ° C, in particular at a temperature between 250-350 ° C, because at at this temperature the devulcanization proceeds very quickly, there will be little degradation of the main chains of the copolymer and a devulcanized product is formed which is easy to reuse.

The time the rubber is heated is usually less than 5 hours, preferably less than 3 hours, more preferably less than 1 hour, and even more preferably less than 30 minutes. At a higher temperature, a shorter time is generally required to obtain a devulcanized product that is reusable than at a lower temperature.

The heating of the rubber preferably takes place in a substantially oxygen-free atmosphere. This can be obtained, for example, by saturating the reaction vessel in which the rubber to be devulcanized is located with nitrogen.

Rubber articles obtained by vulcanizing the copolymer, optionally in the presence of other substances such as, for example, fillers, additives, plasticizers and oils, with a sulfur-containing compound, are preferably pretreated before being devulcanized.

1 y i O J O 0 I

- 4 - the equipment known in the literature for shredding, grinding, cutting, grinding and crumbling rubber or plastic articles.

As α-olefins suitable for use as a monomer in addition to ethylene can be mentioned: propylene, butene-1, pentene-1, hexene-1, octene-1 or its branched isomers, such as for example 4-methylpentene-1 , and further styrene and α-methylstyrene. Mixtures of these olefins can also be used; propylene and / or butene-1 are preferred.

The ethylene / propylene molar ratio will generally be between 5: 1 and 1: 5. Preferably between 3: 1 and 1: 1.

A group X polymerizable by a coordination catalyst is a group containing at least one carbon-carbon double bond which can be polymerized in the presence of a coordination catalyst, for example a Ziegler-20 Natta catalyst or a metallocene catalyst.

Examples of a polymerizable group X which can be polymerized with the aid of a coordination catalyst are vinyl, norbornyl, dinorbornyl and dicyclopentadienyl.

R ° is a chain with 2-20 C atoms and at least one carbon-carbon double bond, none of the C atoms of the double bond being part of a ring structure. Preferably R ° is selected from chains complying with one of formulas II or III: 1013155 i - 5 - R3 R3 R4 Rs R7 R8

- I III II

- [ch2] n — C --- C --- C = C --- C - C = C (II)

5 II I II

OU R2 Rg R ^ I L. Jf L JqL Jg R10 L Jp 10 - [CH2] r — C — R14 (III)

II

CH

15 I

R10 where R18, R8, R10, and R14 may be the same or different and hydrogen or a hydrocarbon group containing 1-5 C atoms; R9 represents a hydrogen or a hydrocarbon group with 1-5 C atoms when p and q are equal to 1 or a group of the formula - (CH2) ni-CR11 = CR12Ri3 when p and q are not equal to 1, where Rh -R12 may be the same or different and represent hydrogen or a hydrocarbon group with 1-5 C atoms and R13 represents a hydrocarbon group with 1-5 C atoms; p and q are independently 0 or 1, but are not simultaneously 0; F = 0-5, but if p and q are equal to 1 then f cannot be 0; g = 1-6; n = 1-5; r = 0-5 and m = 1-5.

Monomer units of a polyunsaturated compound of formula (I) serve to introduce unsaturation into the copolymer; and can be aliphatic or alicyclic.

10131 '? - 6 -

An aliphatic polyunsaturated compound, is preferably a compound of formula (I) wherein X is vinyl and R ° satisfies formulas (II) or (III) and wherein the carbon-carbon double bonds present are conjugated or non-conjugated. conjugated. Preferably, the carbon-carbon double bonds are unconjugated. Examples of aliphatically conjugated polyunsaturated compounds are: 1,3-butadiene, 10 isoprene, 2-ethylbutadiene-1,3 and piperylene. Examples of aliphatic non-conjugated polyunsaturated compounds are: 1,4,9-decatrienes, 1,4-hexadiene, 1,5-hexadiene, 4-methyl-1,4-hexadiene, 4-ethylidene-10-methyl-1 , 6,9-15 decatriene, 9-methyl-1,5,8-nonatriene, 4-ethylidene-1,7-nonadiene, 4-ethylidene-8-methyl-1,7-nonadiene. 1,4-Hexadiene or 4-ethylidene-8-methyl-1,7-nonadiene is preferably used as the aliphatic non-conjugated polyunsaturated compound.

An alicyclic polyunsaturated compound, is preferably a compound of the formula (I) wherein X can be both mono- and polycyclic, preferably norbornyl, dinorbornyl and dicyclopentadienyl and R 0 satisfies formulas (II) or 25 ( III) and wherein the carbon-carbon double bonds present may be conjugated or non-conjugated. Preferably, the carbon-carbon double bonds are unconjugated. Examples of such polyunsaturated compounds are non-conjugated alicyclic dienes, alicyclic trienes or alicyclic tetraenes. Mixtures of the polyunsaturated compounds described above can also be used.

For example, monomer units of a polyunsaturated compound are present in the copolymer in amounts of up to 30% by weight, preferably up to 15% by weight, especially between 2 and 10% by weight, relative to the other monomer units.

The vulcanization of the copolymer is necessary to obtain a rubber article that is dimensionally stable.

This form-retaining article is obtained by chemically cross-linking freely movable macromolecules of the copolymer, so that the article becomes, as it were, one large macromolecule or network.

Devulcanization is understood to mean reducing or reducing the number of nodes until a product is formed that is suitable for reuse. For example, it is possible to mix the devulcanized rubber with an as yet unvulcanized copolymer and then extrude or roll the mixture of the devulcanized rubber and the as yet unvulcanized copolymer thus obtained into a product. It is also possible, if the number of nodes of the rubber has been greatly reduced as a result of the devulcanization, the devulcanized rubber as such can be processed into a product in the above manner.

The number of nodes of the rubber is reduced by heating the rubber for a certain period of time. As a measure of the progress of this devulcanization process, the amount of polymer dissolving in a suitable solvent such as 1013155-8 - for example tetrahydrofuran (THF) can be taken. The amount of polymer that can be dissolved by extraction with THF depends on the number of broken rubber nodes. The greater the amount of dissolved polymer, the more nodes will be broken.

The invention also relates to a devulcanized rubber, the amount of soluble polymer in tetrahydrofuran of which is greater than 20 wt.%, Preferably greater than 30 wt.%, In particular greater than 50 wt.%.

As a devulcanizing agent, any commercially applicable devulcanizing agent can be used as long as it is capable of breaking the 15 nodes in a sulfur compound vulcanized rubber. It is not necessary for the devulcanizing agent to break all nodes in the vulcanized rubber.

The devulcanizing agent should preferably disconnect at least a portion of the nodes.

Preferably, devulcanizing agents are used selected from the group containing aromatic and aliphatic disulfides, thiols and amines. Examples of aromatic and aliphatic disulfides are: diphenyl disulfide, dixylyl disulfide, dibenzyl disulfide and dibutyl disulfide. Diphenyl disulfide is preferably used.

The amount of the vulcanizing agent added is preferably between 0 and 30 wt%, more preferably between 0 and 5 wt%.

The invention also relates also to Ki2 *; ·) 0 - 9 - on a mixture of the devulcanized rubber obtained by the described method and an as yet unvulcanized rubber, vulcanizing agent, oil, carbon black and optionally additives. The usual techniques and equipment can be used for mixing. The mixing operations are preferably carried out at a temperature between 50 ° C and 120 ° C. During mixing, if desired, the usual additives and additives for the polymer composition can be added, for example stabilizers, dyes, processing aids, for example release agents and flame-retardant additives and fillers or reinforcing (fiber) materials.

The mixture according to the invention can be used in the usual applications of vulcanized ethylene-alpha-olefin-diene copolymers. Examples of such applications are bicycle tires, mats, cable jackets, hoses and buffers.

The invention will now be further explained by means of the following examples and comparative examples, without being limited thereto.

The amount of soluble polymer is determined as follows. After extraction with acetone, the rubber is dried in a vacuum oven. The dry, devulcanized rubber, now free from devulcanizing agent and oil, is weighed and then extracted with tetrahydrofuran in a Soxhlet extractor under nitrogen and excluding light for 96 hours. After extraction, the rubber is again dried in a vacuum oven and weighed 1013155-10. The difference gives the amount of soluble polymer. This amount is expressed as a percentage of the devulcanized rubber sample for samples without carbon black and free from devulcanizing agent and oil. In the case of rubber with carbon black, the amount is expressed as the percentage of the polymeric part present in the rubber free from the vulcanizing agent and oil.

Example I

In an internal mixer, 50 parts per hundred (dph) Sunthene 4240 oil and 80 dph carbon black N330 were added to Nordel 1040 (an EPDM polymer with 3 wt% 1,4-hexadiene and 54 wt% ethylene) and mixed.

The mixture was then mixed on a laboratory mixer with 5 dph zinc oxide, 1 dph stearic acid, 0.5 dph mercaptobenzothiazole, 1 dph tetramethylthiuram disulfide and 1.5 dph of a sulfur compound and then heated.

The amount of still soluble polymer of the vulcanized rubber in tetrahydrofuran thus obtained was between 1.9 and 3.2% by weight.

The vulcanized rubber was then saturated with nitrogen in the closed oven in the presence of 2.5 wt% diphenyl disulfide and heated at 266 ° C for 2 hours under a pressure of 7.6 MPa.

After devulcanization, the amount of soluble polymer was measured as a measure of the compulseness of the devulcanization. The amount of soluble polymer in tetrahydrofuran was 55 ± 2% by weight with respect to the polymeric part.

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Example II

Example I was repeated, except that the amount of diphenyl disulfide was varied as indicated in Table 1.

Table 1: Content of soluble polymer in THF as a function of the amount of diphenyl disulfide e.g. Diphenyl disulfide soluble polymer wt% wt% _____ _ ______ _____ _ _ _____ _ 55 + 2 11.4 375 «55 11.5 §75 755 10

Example III

Example I was repeated, except that the temperature was varied as indicated in Table 2.

Table 2: Content of soluble polymer in THF as a function of the temperature e.g. Temperature soluble polymer ° C wt.% III.1 Ï8Ö ÏÖ III .2 2ÖÖ 20 ± 5

V

e.g. Temperature soluble polymer - 12 - ° C wt.% III.3 266 55 ± 2 III .4 3ÖÖ 73 ± 13 III.5 35Ö »100

Example IV

Example I was repeated, with the difference that the time was varied as indicated in Table 3.

Table 3: Content of soluble polymer in THF as a function of time 10 ex. Time soluble polymer min wt% _____ __ 55 VI .2 60 55 VI.3 Ï2Ö 55 VI.4 Ï8Ö 55

Example V

Example I was repeated, except that no Sunthene 4240 oil and carbon black N330 were added to the EPDM polymer, the devulcanization temperature was 200 ° C and the amount of diphenyl disulfide was varied as indicated in Table 4.

1013155

Table 4: Content of soluble polymer in THF as - 13 - function of the amount of diphenyl disulfide e.g. Diphenyl disulfide soluble polymer wt% wt% __ _ _ V. 2 2T5 22 V. 3 275 33 Ύ7Ζ 375 45 __ _ - 5

Example VI

In an internal mixer, an EPDM polymer with 3.3 wt% 4-ethylidene-8-methyl-1,7-nonadiene (EMN) and 56 wt% ethylene, 50 dph Sunthene 10 4240 oil and 80 dph carbon black N330 added and mixed.

The mixture was then mixed on a laboratory mixer with 5 dph zinc oxide, 1 dph stearic acid, 0.5 dph mercaptobenzothiazole, 1 dph tetramethylthiuram disulfide and 1.5 dph of a sulfur compound 15 and then heated.

The amount of still soluble polymer of the vulcanized rubber in tetrahydrofuran thus obtained was between 2 and 3% by weight. The vulcanized rubber was then saturated with nitrogen in the closed oven in the presence of 2.5 wt% diphenyl disulfide and heated at 266 ° C for 2 hours under a pressure of 7.6 MPa. After devulcanization, the amount of soluble polymer was measured as a measure of the compulseness of the devulcanization. The amount of soluble polymer in tetrahydrofuran in the proportion of the polymeric part was 58% by weight.

Example VII

Example VI was repeated, except that the amount of diphenyl disulfide was varied as indicated in Table 5.

Table 5: Content of soluble polymer in THF as a function of the amount of diphenyl disulfide eg. Diphenyl disulfide soluble polymer wt. % wt. % VII.1 Ö 43 VII .2 ÏT5 68 VI 1.3 2T5 72 _____ _ - _____ _ _

Example VIII

Example VI was repeated, except that the temperature was varied as indicated in Table 6.

Table 6: Content of soluble polymer in THF as.

- 15 - function of the temperature e.g. Temperature soluble polymer ° C wt% _____ _ _ VIII.2 2ÖÖ 23 VIII.3 266 58 VIII.4 3ÖÖ 77 VIII. 5 35Ö ÏÖÖ 5

Example IX

Example VI was repeated, except that the time was varied as indicated in Table 7.

10

Table 7: Content of soluble polymer in THF as a function of time eg. Time soluble polymer min wt% IX. 1 30 58 IX.2 60 58 IX. "3 120 58 IX.4 180 58 15

Example X.

Example VI was repeated, with the difference that no Sunthene 4240 oil and carbon black N330 were added to the EPDM polymer, the devulcanization temperature was 200 ° C and the amount of diphenyl disulfide was varied as indicated in Table 8.

Table 8: Content of soluble polymer in THF as a function of the amount of diphenyl disulfide e.g. Diphenyl disulfide soluble polymer wt% wt% X.1 Ö Ï8 __ _ _ T71 275 43 X.4 JT5 45 X. 5 STÖ 52 10

Comparative example A

In an internal mixer, Keitan® 4802 (an EPDM polymer with 4.5 wt% 5-ethylidene-2-15 norbornene and 49 wt% ethylene) was added 50 dph Sunthene 4240 oil and 80 dph carbon black N330. The mixture was then mixed with 5 dph zinc oxide, 1 dph stearic acid, 0.5 dph mercaptobenzothiazole, 1 dph tetramethylthiuram disulfide and 1.5 dph of a sulfur compound on a laboratory mixer and then heated.

The amount of still soluble polymer of the vulcanized rubber in tetrahydrofuran thus obtained was 1.0% by weight.

5 U i <.: - '· - - 17 -

The vulcanized rubber was then saturated with nitrogen in the closed oven in the presence of 2.5 wt% diphenyl disulfide and heated at 266 ° C for 2 hours under a pressure of 7.6 MPa. After devulcanization, the amount of soluble polymer was measured as a measure of the completeness of the devulcanization. The amount of soluble polymer in tetrahydrofuran was 18% by weight.

Table 9: Content of soluble polymer in THF as a function of the amount of diphenyl disulfide eg. Diphenyl disulfide soluble polymer wt% wt% A.l Ö 9 A. ~ 2 ÏT5 14 AT3 275 18 __ __ - X5 5TÖ Ï8

Table 10: Content of soluble polymer in THF as a function of the temperature eg. Temperature soluble polymer ° C wt.% A. 6 Ï8Ö 2 A.7 200 6 __ _ __ A.9 300 28 - A.10 35Ö 38 1013155

Table Ί Ί: Content of soluble polymer in THF as - 18 - function of time eg. Time soluble polymer min wt% A. 11 30 18 A.12 60 18 A.13 Ï2Ö Ï8 A. 14 18Ö Ï8 5

.Comparative example B

In an internal mixer, 50 dph Sunthene 4240 oil and 80 dph 10 carbon black N330 were added to Keltan® 820 (an EPDM polymer with 4.5 wt.% Dicyclopentadiene and 55 wt.% Ethylene) and mixed. The mixture was then mixed on a laboratory mixer with 5 dph zinc oxide, 1 dph stearic acid, 0.5 dph mercaptobenzothiazole, 1 dph tetramethylthiuram disulfide and 1.5 dph of a sulfur compound 15 and then heated.

The amount of still soluble polymer of the vulcanized rubber in tetrahydrofuran thus obtained was 4.0% by weight.

The vulcanized rubber was then saturated with nitrogen in the presence of 2.5 wt% diphenyl disulfide in a closed oven and heated at 266 ° C for 2 hours under a pressure of 7.6 MPa. After devulcanization, the amount of soluble polymer was measured as a measure of the completeness of the devulcanization. The amount of soluble polymer in 10'-19-tetrahydrofuran was 21% by weight.

Table 12: Content of soluble polymer in THF as a function of the amount of diphenyl disulfide 5 ex. Diphenyl disulfide soluble polymer wt% wt% B.1 ö ΓΪ 1Γ2 ÏT5 16 B.3 2T5 21 B.4 3T5 '25 B.5 5TÖ 25

Table 13: Content of soluble polymer in THF as a function of temperature 10 ex. Temperature soluble polymer 0 c wt. % B.6 180 ÏÖ B. 7 2ÖÖ 20 B.8 266 21 B.9 3ÖÖ 31 B.10 35Ö 45 1013155

Table 14: Content of soluble polymer in THF as - 20 - function of time eg. Time soluble polymer min wt% B.11 30 21 B. 12 60 21 B.13 Ï2Ö 2Ï B.14 Ï8Ö 2Ï 5

Comparative example C

Comparative Examples A and B were repeated, except that no Sunthene 4240 oil and carbon black N330 were added to the EPDM 10 polymer, the devulcanization temperature was 200 ° C and the amount of diphenyl disifide was varied.

Table 15: Content of soluble polymer in THF as a function of the amount of diphenyl disulfide 15 ex. Diphenyl disulfide soluble polymer wt. % wt. % A.C.1 Ö Ö7Ï _____ _ _ A.C.3 2T5 0T4 A.C.4 3T5 ÖT6 A. C.5 5TÖ Ï7Ö B. C.1 Ö ÏT5 B.C.2 ΓΤ5 IT5 1 013 '; -5 ex. Diphenyl disulfide soluble polymer - 21 - wt% wt% B.C.3 275 ÏT5 B.C.4 3T5 ÏT5

B.C.5 5TÖ O

1013155

Claims (18)

1. A method for devulcanizing a rubber, which rubber is obtained by vulcanizing a copolymer containing ethylene monomer units, monomer units of an alpha-olefin and monomer units of a polyunsaturated compound using a sulfur-containing compound, by heating the rubber at such a high temperature that devulcanization occurs and a reusable product is obtained, characterized in that a rubber is obtained which is obtained by vulcanizing a copolymer containing monomer units of a polyunsaturated compound of the formula XR °, wherein X is a group of 2-20 carbon atoms polymerizable by a coordination catalyst, R ° contains a chain of 2-20 carbon atoms with at least one carbon-carbon double bond, none of the carbon atoms of the double bond is part of a ring structure. 2. R10 wherein R 1, R 8, R 10 and R 14 may be the same or different and represents hydrogen or a hydrocarbon group with 1 to 5 C atoms; R9 represents a hydrogen 25 or a hydrocarbon group with 1-5 C atoms when p and q are equal to 1 or represents a group of the formula - (CH2) m-CR11 = CR12R13 when p and q are not equal to 1, where Rh-R 12 may be the same or different and represent hydrogen 30 or a hydrocarbon group with 1-5 C atoms and R13 represents a hydrocarbon group with 1-5 C atoms; p and q are independently 0 or 1, but are not simultaneously 0; F = 0-5, but if p and q are equal to 1 then f cannot be 0; 1013155-24 - g = 1-6; η = 1-5; r = 0-5 and m = 1-5. A method according to any one of claims 1, characterized in that the α-olefin is selected from the group containing propene and butene-1. 3. A method according to any one of claims 1-2, characterized in that X is selected from the group containing vinyl, norbornyl, dinorbornyl, dicyclopentadienyl. 4. i * 3 ί · Λ ί yi ö o »O O - 23 - Process according to any one of claims 1 to 3, characterized in that R ° satisfies one of formulas II or III: 5 R3 R3 R4 Rg R7 Rg - I II I II - [CH2] n-C --- C --- C = C --- C - C = C (II) II I II 5. Process according to any one of claims 1-4, characterized in that the amount of monomer units of a polyunsaturated compound in the copolymer is between 2 and 10% by weight. 6. A method according to any one of claims 1-5, characterized in that the heating of the rubber takes place in a virtually oxygen-free atmosphere. A method according to any one of claims 1-6, characterized in that the rubber is heated at a temperature between 150 and 350 ° C. 8. A method according to any one of claims 1-7, characterized in that the rubber is heated at a temperature between 250 and 350 ° C. A method according to any one of claims 1-8, characterized in that the time of heating the rubber is less than 3 hours. 10. A method according to any one of claims 1-9, characterized in that the time of heating the rubber is less than 1 hour. 10 CH R2 Rg Rg I L Jf L Jq L jg RlO L JP 15 - [CH2] r — C — R14 (III) II CH A method according to any one of claims 1-10, characterized in that a devulcanizing agent is added to the rubber. A method according to claim 11, characterized in that the amount of devulcanizing agent added is between 0 and 5% by weight. 13. A method according to any one of claims 11-12, characterized in that the devulcanizing agent is selected from the group containing aromatic and aliphatic disulfides, thiols and amines. t. "n *) o * · C ~ ^ Ij ύ W 8 O ^ - 25 - A method according to any one of claims 11-13, characterized in that the devulcanizing agent is diphenyl disufide. 15. A devulcanized rubber obtainable by the method described in any one of the preceding claims, characterized in that the amount of soluble polymer in tetrahydrofuran is greater than 30% by weight. A devulcanized rubber according to claim 10, characterized in that the amount of soluble polymer in tetrahydrofuran is greater than 50% by weight. 17. A mixture containing an unvulcanized rubber, vulcanizing agent, oil, carbon black and optional additives, characterized in that the mixture contains the devulcanized rubber obtained by the described method. 18. The use of the mixture according to claim 17 for the production of rubber articles 1013155 COOPERATION VêHUHAü (kli; REPORT ON NEWNESS CURRENT OF INTERNATIONAL TYPE IDENTIFICATION OF THE NATIONAL APPLICATION Characteristic of the applicant or of the authorized representative 9730 NL Netherlands »Application no. September 1999 Priority date invoked Applicant INaam) DSM NV Date of the request for an investigation of international type Granted by the Netherlands Institute for International Research to the request for an investigation of international type hr. SN 33822 EN I. CLASSIFICATION OF THE SUBJECT (when using different classifications, indicate all classification symbols) According to International Classification (IRC) lnt.CI.7: c08j11 / 12 c08j11 / 28 c08l23: 16 II. FIELDS OF TECHNIQUE EXAMINED __Minimum documentation examined_ Classification system Classification tools _____ lnt.CI.7: c08j Review of other documentation and minimum documentation to the extent that documents are included in the non-requested areas. M | l NO RESEARCH POSSIBLE FOR CERTAIN CONCLUSIONS (comments on supplement sheet) you i-- I LACK OF UNIT OF INVENTION (comments on supplement sheet) / Pa cm PCT / lSA / 201tai 07.1979 *