AU609775B2 - Diels alder assisted polymers grafting process - Google Patents

Description

AUSTRALIA 609775 Patents Act WOW=T SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: 9 4 I (~Co I .k7 c' ~.aioii 4 ai~d 1 Dr;nLing Lor Priori ty rRelated Art: F*f Of APPLICANT'S REFERENCE: 32,836-F ,Name(s) of Applicant(s): The Dow Chemical Company Address(es) of Applicant(s): 2030 Dow Center, Abbott Road, 'Midland, Michigan 48640, UNITED STATES OF AMERICA.

Address for Service is: PHILLIPS CIU(RNDE £FITZPATRICK Patent and Trade Hark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Complete Specification for the invention entitled: DIELS ALDER ASSISTED POLYMERS GRAFTING PROCESS Our Ref 84161 POF Code: 1037/1037 The following statement Is a full description of this invention, including the best method of performing it known to applicant(s): 6003q/1.-1 1

LOI

Our Ref 84161 POP Code: 1037/1037 6012q/1 iF

I

j

C:

-1 a- DIELS ALDER ASSISTED POLYMER GRAFTING PROCESS 00 00 @0 0

S

0 *0 @6 0 0 0@ *0 This invention relates to a method of grafting an ethylenically unsaturated monomer onto a polyolefin 5 or polyvinyl polymer substrate and particularly to such a method in which a Diels Alder adduct of the monomer to be grafted is employed to provide the source of the ethylenically unsaturated monomer through a retro Diels Alder mechanism.

The grafting of ethylenically unsaturated monomers onto a molten polymer substrate with or without a free radical initiator is well known. For example, methods of grafting monomers such as maleic anhydride onto polyethylene in an extruder are described in U. S. Patents 3,882,194 and 3,873,643.

In many applications, however, the monomer to be grafted is volatile and requires elaborate, complicated and often expensive apparatus and techniques to prevent escape of the volatile monomer from the polymer melt. Usually, the volatile monomer is both toxic and flammable, posing risks to personnel and equipment.

32,836-F

LA

-1A -2- In addition, monomers such as acrylic acid, for example, are too reactive to be conveniently grafted to the polymer. Generally, such graft monomers will homopolymerize to an undesirable extent and not react with the polymer to be grafted to the desired extent.

Further, many monomers are not miscible or soluble in the polymer melt, resulting in poor dispersion of the monomer in the graft polymer product and considerable quantities of the monomer intended to be grafted being homopolymerized.

Further still, many monomers are liquid at room temperature and are consequently difficult to mix with 15 a normally solid polymer substrate and too volatile to mix with a molten polymer substrate.

The present invention avoids the foregoing problems associated with the prior art by employing a 20 Diels Alder adduct of the monomer desired to be grated which decomposes into the monomer to be grafted and conjugated diene at the grafting conditions.

The present invention provides a process of grafting ethylenically unsaturated monomer onto a polyolefin or a vinyl polymer. The process includes the step of mixing a polyolefin or vinyl polymer substrate with a Diels Alder adduct of the ethylenically unsaturated monomer to be grafted. The Diels Alder adduct is stable below 1200C and substantially decomposes into conjugated diene and the ethylenically unsaturated monomer to be grafted at a temperature of from 120 to 3000C.

The method also includes the step of heating the polymer substrate/Diels Alder adduct mixture to a 32,836-F -2- -3temperature of from 120 to 300°C sufficient to substantially decompose the Diels Alder adduct into the conjugated diene and the ethylenically unsaturated monomer to be grafted.

The method further includes the step of inducing graft polymerization of the ethylenically unsaturated monomer onto the polyolefin or vinyl polymer substrate, thereby forming a graft polymer.

Optionally, the method may also include the step of devolatilizing the graft copolymer to remove .0 unreacted Diels Alder adduct, conjugated diene and a ethylenically unsaturated monomer therefrom.

In the practice of the present invention a polymer substrate is mixed and heated with a Diels Alder adduct which decomposes upon heating into conjugated diene and ethylenically unsaturated monomer.

20 The ethylenically unsaturated monomer produced by the decomposition of the Diels Alder adduct is then grafted onto the polymer substrate. If desired, any unreacted Diels Alder adduct and decomposition products thereof may be removed by devolatilizing the graft polymer.

The polymers contemplated as suitable substrates in the present method include polyolefins and vinyl polymers. Polyolefins include, for example, homopolymers and copolymers of one or more olefins such 3 as ethylene, propylene, 1-butene, 1-pentene, 3-methyl- 1-pentene, 1-hexene and 1-octene. Further, the pclyolefins also include olefins copolymerized With relativey minor amounts of monomers copolymerizable therewith, such as, for example: vinyl aryls such as styrene, substituted styrenes, vinyl naphthalene, vinyl 32,836-F -3iI -4- 9 9 99

S

S

6 S. S and vinylidene halides such as vinyl chloride anc' vinylidene bromide; vinyl esters such as vinyl acetate, vinyl propionate and vinyl chloroacetate; acrylic and a-alkyl acrylic acids, and the alkyl esters, amides and nitriles thereof, such as acrylic acid, chloroacrylic acid, methacryliac acid, methyl acrylate, acrylamide, N-methyl acrylamide, acrylonitrile, choroacrylonitrile and methacrylonitrile; alkyl esters of maleic and fumaric acid such as dimethyl maleate and diethyl fumarate; vinyl alkyl ethers and ketones such as vinyl methyl ether, vinyl ethyl ether, 2-chloroethyl vinyl ether, methyl vinyl ketone and ethyl vinyl ketone; and other copolymerizable monomers such as carbon Smonoxide.

Preferred polyolefins include low density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-propylene rubbers and polypropylene.

Suitable vinyl polymers include, for example, homopolymers and copolymers of one or more vinyl compounds such as: vinyl aryls such as styrene, 25 substituted styrenes and vinyl napthalene; vinyl and vinyldene halides such as vinyl chloride, vinylidene chloride and.vinylidene bromide; vinyl esters such as vinyl acetate, vinyl propionate and vinyl chloroacetate; acrylic and a-alkyl acrylic acids, and the alkyl esters, amides and nitriles thereof, such as acrylic acid, chloroacrylic acid, methacrylic acid, methyl acrylate, acrylamide, N-methyl acrylamide, acrylonitrile, chloroacrylonitrile and methacrylonitile; and vinyl alkyl ethers and ketones such as vinyl methyl ether, vinyl ethyl ether, 2chloroethyl ether, methyl vinyl ketone arid ethyl vinyl 32,836-F -4ketone. Further, the vinyl polymers also include vinyl compounds copolymerized with relatively minor amount of monomers copolymerizable therewith such as, for example: olefins such as ethylene, propylene and 1butene; alkyl esters of maleic and fumaric acid such as dimethyl maleate and diethyl fumarate; and other copolymerizable monomers such as carbon monoxide.

Preferred vinyl polymers include polystyrene and block copolymers of styrene and butadiene.

The Diels Alder adducts contemplated as suitable in the method include those which decompose upon heating into conjugated diene and ethylenically o*o 15 unsaturated monomer. The Diels Alder adduct must not substantially decompose below 120°C in order to permit adequate mixing of the Diels Alder adduct with the polymer substrate before grafting, and must substantially decompose below 300 0 C to avoid degradation S of the substrate polymer. As used herein with respect to the Diels Alder adduct, the phrase "not substantially decomposed" means that not more than about 10 percent decomposed into the diene and carbonyl monomer constituents, and the phrase "substantially decomposed" means that at least 90 percent of the adduct is so.decomposed.

The Diels Alder adduct is preferably also substantially nonvolative below 120 0 C to further facilitate blending of the adduct with the polymer substrate. As used herein, the term "nonvolatile" means having a vapor pressure of about 0.5 atm or less at the specified temperature.

32,836-F -6- The thermal decomposition products of the Diels Alder adduct include conjugated diene and ethylenically unsaturated monomer. Contemplated suitable diene decomposition constituents include, for example: acyclic diens such as 1,3-butadiene, isoprene, 1,3pentadiene, 1,3-hexadiene, 2,4-hexadiene and 1,3,5hexatriene; cyclic dienes such as 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-methyl-1,3-cyclohexadiene, and methyl-1,3-cyclohexadiene; and heterocyclic dienes such as furan and thiophene.

Contemplated ethylenically unsaturated monomers produced from thermal decomposition of the Diels Alder adduct generally conform to the formula RIR2C=CHR 3 15 wherein RI is hydrogen, methyl or ethyl, R 2 is hydrogen, methyl, ethyl or vinyl, and R 3 is hydroxyl, Scarboxyl, cyano, formyl, acetyl, propanoyl, phenyl, trialkoxysilyl, hydroxyphenyl, isocyanato, pyridinyl or 20 amino.

Specific representative examples of S ethylenically unsaturated monomers produced from the g thermal decomposition of the Diels Alder adduct include: conjugated ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid, angelic acid, senecoic acid, P-vinylacrylic acid, fumaric acid, itaconic acid and glutaconic acid; conjugated ethylenically unsaturated carboxylic acid anhydrides such as maleic anhydride, itaconic anhydride and glutaconic anhydride; and alkyl vinyl ketones such as methyl vinyl ketone and ethyl vinyl ketone.

The Diels Alder adduct may generally be prepared by reacting the conjugated diene and the 32,836-F -6- -4 1 -7ethylenically unsaturated monomer under reaction conditions effective to form the adduct.

Specific representative examples of suitable S Diels Alder adducts and their respective conjegated diene and ethylenically unsaturated monomer thermal decomposition products are listed in Table I.

TABLE I Decomposition Products Adduct Diene Monomer 5-norbornene-2- cyclopentadiene P-vinylacrylic acid acrylic acid 15 1-methoxybicyclo- l-methixy-1,3- vinyl methyl ketone oct-5-en-2- cyclohexadiene dimer S yl methyl ketone 5-norbornene-2- 1,3-cyclopentadiene acrylic acid carboxylic acid dimer .The mixing of the polymer substrate and the Diels Alder adduct may be accomplished in either solid or molten form as by, for example, dry blending, Banbury mixing, in a roll mill or in a mixing extruder.

Masterbatches which contain a relatively high percentage of the Diels Alder adduct in a polymer substrate may also be employed by mixing the materbatch with the polymer substrate to obtain the desired proportion of Diels Alder adduct. Preferably, the mixing is done at a temperature below which the Diels Alder aaduct is volatile and below which the Diels Alder adduct is not substantially decomposed.

The mixture is then heated to a temperature at which the Diels Alder adduct substantially decomposes into the diene and monomer constituents, but not above 32,836-F -7iii I, I -8- 300 0 C in order to avoid degradation of the polymer substrate. Preferably, the temperature to which the mixture is heated is from 1500 to 250 0

C.

Graft polymerization of the monomer onto the polymer substrate in the molten mixture is then induced by the heating alone, but is preferably induced by the heating in the presence of a free-radical catalyst such as air, peroxides or actinic light, and more preferably also under high shear conditions.

.The mixing, heating and inducing graft polymerization is preferably done simultaneously, either on a batch or continuous basis. In a preferred 15 embodiment, the process is effected with a screw-type extruder.

Generally, from 0.2 to 5 parts by weight of the Diels Alder adduct are mixed with 100 parts by weight 20 of the polymer substrate, preferably from 1 to 3 parts oy weight of the adduct per 100 parts polymer substrate.

O S S S Examole 1 Using a Haake Buchler Rheocord System 40 mixing device, 40 g of an ethylene-octene LLDPE having a density of about 0.920 g/cc and a melt index of 6.6 were fluxed in the mixing head at 50 rpm at a temperature of 220C. Over a period of 1 minute, 8.2 mg-moles of 5-norborene-2-carboxylic acid and 30 pl (2.8 mg) of 2,5-dimethyl-2,5-di(t-butyl peroxy)hex-3yne were added to the fluxing LLDPE with a syringe through an injection ram modified for this purpose.

The mixer speed was then increased to 200 rpm for 6 32,836-F -8i- -9minutes. The graft copolymer product was then removed from the mixer and cooled.

The graft copolymer product was dissolved in xylene at 10°C, precipitated with acetone, filtered, and dried in a vacuum oven at 60°C for 14 hours to remove residual low molecular weight materials. By titi'ation in 3:1 xylene/butanol with tetra-n-butyl ammonium hydroxide (1.OM in methanol) using thymol blue as an indicator, the graft copolymer product had an acrylic acid content of 0.27 weight percent.

S* The above procedure was repeated except that 8.2 mg-moles of acylic acid were used instead of 15 norborene-2-carboxylic acid. The resulting g graft copolymer had an acrylic acid content of 0.24 weight percent. This example demonstrates that equivalent grafting of a conjugate ethylenically unsaturated carbonyl such as acry ia acid may be achieved by using 20 S 20 a Diels Alder adduct t' ereof.

Examole 2 Using a Brabender mixer capable of mixing aliquots of up to 50 g of polymer, 40 g of HDPE (0.962 g/cc, melt index 10) were added to the mixing head and allowed to melt for about 30 seconds at 175 C at 200 S rpm. Over a period of 30 seconds, 21.7 mg-moles of norbornene-2-carboxylic acid were injected into the mixing chamber. After allowing 15 seconds for mixing, pl of a 50 weight percent solution of dicumyl peroxide in methyl ethyl ketone were injected. After mixing an additional 3 minutes, the grafted copolymer was removed from the chamber and allowed to cool.

The graft copolymer product was dissolved in xylene at 100°C, precipitated with acetone, filtered and 32,836-F -9- I i I :I dried in a vacuum oven 70°C for 14 hours to remove residual low molecular weight materials. By infrared spectroscopy, the incorporated acylic acid content was determined to be about 0.14 percent by weight. The graft copolymer had a melt index of 4.08.

The above procedure was repeated except that 21.7 mg-moles of acrylic acid were used instead of the 5-norbornene-2-carboxyic acid. The resulting graft copolymer had an acrylic acid content determined by infrared spectroscopy of about 0.27 weight percent.

However, the melt index of this material was 0.88, indicating that substantially more crosslinkage *o occurred when acrylic acid was used instead of the 15 Diels Alder adduct thereof.

Examole 3 The procedure of Example 2 was repeated with 20 24.9 mg-moles of 1-methoxybicyclo[2.2.2]oct-5-ene-2-yl methyl ketone instead of 5-norbornene-2-carboxylic acid, and 100 il of 2,5-dimethyl-2,5-di(t-butyl- I peroxy)hex-3-yne were added in place of the 50 weight percent dicumyl peroxide in methyl ethyl ketone. By IR spectroscopy, the resulting graft copolymer contained about 0.15 percent vinyl methyl ketone by weight.

Examole 4 To demonstrate that various Diels Alder adducts are suitably employed in the present method, the IR absorption of various Diels Alder adducts were determined and compared with the saturated Diels Alder adduct and with graft HDPE copolymers thereof. The monomers were grafted to high density polyethylene (0.954 goo, 5 melt index) in a Haake Buchler System 32,836-F i -11mixing device by introducing 38 g of the HDPE into the mixing head at 300 0

C.

Following a one minute melt time, 204 mg-moles S of the Diels Alder adduct (or maleic anhydride monomer) to be examined were added to the mixing head and mixed with the HDPE for 15 minutes at 250 rpm rotor speed.

The graft copolymer was then removed from the chamber, cooled, dissolved in hot 1,2,4-trichlorobenzene at 2 weight percent, precipitated with an equal volume of 2butanone, filtered and dried in a vacuum oven to substantially remove residual monomer. The graft copolymers were then analyzed by infrared spectroscopy to determine the peak carbonyl absorption wavelengths.

The data is presented in Table II along with the peak carbonyl absorption values for the adduct and the saturated adduct.

o.

S*

0 32,836-F -11- -12- Table II Monomer Adduct/ No. Monomer 1 Maleic anhydride 2 Tetrahydrophthalic anhydride Unsaturated Saturated Absorption absorption

LLDPE

Graft Copolymer Absorptions 1797, 1873.5 0* S S

S

OS Be S S

S

S.

S S

S

0

S

@5005

S

3 Bicyclo[2.2. 1] 2 ,3-dicarboxylic anhydride 4 7-Oxabicyclo 2. 2. 1]hept- 5-ene-2, 3di car bo xyll c anhydride 5 6-Methylbicyclo 11-hept- 5-ene-2, 3dicarboxylic anhydr ide 6 B icyclo(2,2.2j oc 2, 3-dicarboxylic anhyd ride 1788, 1863 1780, 1847 1775, 1856 1795, 1865 1792, 1863 1798, 1866 1788, 1865 1795, 1864 1795,1872 1795.5, 1874 1785, 1863 1796,1873

OS

S 5S 5* 0 5

S.

OS

S. S B.

1788, 1865 1798, 1874

S

.555.5

S

0

*SS*SS

S

7 6-Methyltetrahydropht halic anhydride 8 B icycl1o2.2,21 oct-7-ene- 2,3,5,6tetracarboxylic acid dl anhydride 1773, 1840 1780, 1860 1797, 1874 1778B-178 8, 18 57 Note for Tathie II: NA saturated absorptions not determnd 32)836-s .1- -12- .4 9

U

U

4 *0

U

0 *1 Se 4

SU

*C 4 4 4* 6 -13- By comparing the IR absorption of various graft copolymers of Diels Alder adducts, it is seen either that the decomposition products (maleic anhydride) were grafted (as with monomers 3 to the Diels Alder adduct itself was grafted (as with monomer or the adduct did not result in any grafting at all (as with monomer depending on the decomposition temperature of the adduct. It is believed that monomer No. 8 did not yield any maleic anhydride grafting because of its relatively high decomposition temperature, whereas monomer No. 2 did not graft at all because of its relative volatility.

Examole A series of tests were run to demonstrate a technique for screening the suitability of proposed Diels Alder adducts for use in the present method. A 38.1 cm OV-17 gas ohromatograph column was used in a 20 2 Finnigan 3200 GC-MS at 100°C. A Pyroprobe pyrolysis chamber was connected to the unit as the injection point. Samples of the Diels Alder adduct to be tested were placed in quartz tubes and pyrolysis was incurred for a period of 10 seconds at a predetermined temperature. Helium flowing through the Pyroprobe chamber carried the decomposition products onto the gas chromatrograph column and then to the mass spectrometer for identification. The results are presented in Table

III.

32,836-F -13i; 404440 S S f i i- -1)4- TABLE III Diels Alder Adduct 6* OS S

S

56 b~ *o a 6 *8 *6 9 466546

U

-0 5-norbornene-2-acrylic acid l-methoxybicyclo[2 2. 2joct- 5-ene-2-yl-inethyl ketone 5-norborene-2-carboxylic acid 5-norbornene-2-carboni trule 1 5 5-porbornene-2-carboxaldehyde 5-norbornene-2-ol cyclohex-4-ene-.l, 2-dicarboxylic anhydride 1-methoxybicyclo[2 2. 2]oct- 20 5-ene-2-carbonitrile Result of Pyrolvsis Decomposed into f3-vinyl acrylic acid and cycloperitadiene at 200'C Decomposed into vinyl methyl ketone and the dimer of 1methoxycyclohex-1,3-diene a, 300 0

C

Decomposed into acrylic acid and the diner of cyclopentadiene at 200'C Stable to 300 0

C

Stable to 300 0

C

Stable to 300 0

C

Stable to 450'C Stable 30 0 0

C

between 100 and 4* 4* 9 6 46 *6 q 4@ 320836-F -1 14~

L

Claims (11)

1. Grafting process comprising the steps of: mixing an olefin or vinyl polymer substrate and a Diels Alder adduct which does not substantially decompose S below 120 C and substantially decomposes at a temperature of from 120 C to 300 C into conjugated diene and ethylenically unsaturated monomer of the formula R 1 R 2 CC=CHR 3 wherein R1 is hydrogen methyl or ethyl, R 2 is hydrogen, methyl, ethyl or vinyl, and R 3 is hydroxyl, carboxyl, cyano, formyl, acetyl, propanolyl, phenyl, trialkoxysilyl, hydroxyphenyl, isocyanato, pyridinyl or amino and wherein R2 and R 3 may form an anhydride group; 0 0* NJK T| 1. li-I; 1- ;1 ;i t- r -TS e--1-a-Hn s-d-e-£-i-B-i-ng-h-h a s-i -l-s 1. Grafting process comprising the steps of: mixing an olefi or vinyl polymer substrate and a Diels Alder adduct w ich does not substantially decompose below 120 0 C and/substantially decomposes at a temperature of from 120 C to 300 0 C into conjugated diene and ethylenically unsaturated monomer of the formula R 1 R 2 C=CHR 3 wherein 1 is hydrogen methyl or ethyl, R 2 is hydrogen, methy, ethyl or vinyl, and R 3 is hydroxyl, carbo 1, cyano, formyl, acetyl, propanolyl, phenyl, trial xysilyl, hydroxyphenyl, isocyanato, ,nvridinY1 or min heating the mixture to a temperature of from 120°C to 300°C sufficient to substantially decompose the Diels Alder adduct into the conjugated diene and the ethylenically unsaturated monomer; and inducing graft polymerization of the ethylenically unsaturated monomer onto the polymer substrate, thereby forming a graft copolymer.

2. Process of Claim 1, wherein the polymer substrate is a high density polyethylene, low density polyethylene, liner low density polyethylene, ethylene- propylene rubber, polypropylene, polystyrene or a styrene-butadiene block copolymer. 32,836-F -16-

3. Process of Claims 1 or 2, wherein the Diels Alder adduct undergoes the substantial decomposition at a temperature of from 150 0 C to 250 0 C.

4. Process of any one of Claims 1 to 3, wherein R 3 is carboxyl, formyl, acetyl or propanoyl.

Process of any one of Claims 1 to 4, further comprising the step of: devolatilizing the graft copolymer to substantially remove therefrom unreacted Diels Alder adduct and decomposition products thereof.

6. Process of any one of Claims 1 to 1 wherein the ethylenically unsaturated monomer is 15 acrylic acid, P-vinylacrylic acid or vinylmethyl ~ketone.

7. Process of Claim 6, wherein the Diels Alder adduct is 5-norbornene-2-carboxylic acid, norbornene-2-acrylic acid or 1-methoxybicyclo[2.2.2]oct- 5-ene-2-yl methyl ketone.

8. Process of Claim 7 wherein the polymer U. substrate is: mixed at a high shear rate in the presence S of free radical catalyst with from 0. to 10 parts by weight, per 100 parts by weight of the polymer substrate of Diels Alder adduct.

9. Process of Claim 8 wherein from 0.2 to parts by weight of the Diels Alder adduct are mixed with 100 parts by weight of the polymer substrate.

10. Proces of Claim 9, wherein from 1 to 3 parts by weight of the Diels Alder adduct are mixed with 100 parts by weight of the polymer substrate. 3ATn- n PF a- JO 1A PHILLIPS SONDE FITZPATRICK Attorneys for: THE DOW CHEMICAL CO 32,836-F -17-

11. A process according to claim 9 substantially as hereinbefore described with reference to any one of the examples. DATED: 13 February 1991 PHILLIPS ORMONDE FITZPATRICK Attorneys for: Voe THE DOW CHEMICAL COMPANY aO 0 *0 0 S so 0 V* S 1AS *.Irv/ 5 P 0