1 This Invention relates to a new functlonalized polypropylene

2 composition and a new and improved process for the

3 functionalization of polypropylene, particularly the aleation of

4 polypropylene.

5 Brief Description of the Prior Art

₆ To prepare polypropylene for certain end-use applications it - _j is necessary to functionalize the polymer, I.e., to incorporate

8 functional groups such as maleic anhydride onto the polypropylene

9 polymer chains. The reaction of maleic anhydride with 0 polypropylene is well known in the art. Examples of the prior art 1 are U.S. Patent Nos. 4,404,312; 4,506,056; 3,414,551; 4,370,450; 2 and 4,639,495. European Patent application 0225 186 is another 3 example of a method of grafting maleic anhydride onto 4 polypropylene. In the prior art, the maleation of polypropylene 5 has been accomplished by the use of free radical initiators such 6 as a peroxide Initiator to induce maleation. However, the prior 7 art peroxides which have been used for functionalizing 8 polypropylene cause substantial degradation of the molecular 9 weight of the maleated polypropylene. In an attempt to avoid 0 molecular weight degradation of the maleated polypropylene the i prior art methods employed low levels of peroxide initiator. See, 2 for example, U.S. Patent No. 4,404,312 which states that the 3 organic peroxide should not be more than about 0.1 percent by weight, and preferably not more than 0.01 percent by weight of the polypropylene to be reacted. As a result, 1n the prior art, the extent of maleation of the polypropylene has been restricted. Other attempts to avoid the molecular weight degradation require the use of a third ingredient, such as styrene, which becomes a part of the polymer, or require the use of a catalyst such as N.N-dialkylethanolamine, or other nitrogen, phosphorus, or sulfur

containing compounds. Examples of such Ingredients are found 1n U.S. Patent No. 4,506,056 and EPO Application 0225 186. Summary of the Invention The present invention is a novel composition wherein the molecular weight of a functionalIzed polypropylene product Is greater than heretofore obtained with the prior art radical initiators, and a novel functionalization process wherein minimal molecular weight degradation of the polypropylene occurs during a radical Initiated functionallzation process. This is accomplished by the use of a selected class of peroxides which have been found to produce significant grafting of unsaturated monomers useful for functional1zing polypropylene, such as maleic anhydride, hi ic anhydride, acrylic add, methacryϋc add, vlnyltrimethoxysllane,. acrylamide, itaconic add, maleic acid, fumaric acid, monomethyl maleate, monoethyl aleate, fumaric anhydride, vinyl amines and amides, and other substituted vinyl monomers that are capable of free radical polymerization, onto polypropylene without causing significant molecular weight degradation of the polypropylene. Polypropylene has many attractive characteristics such as a high melting temperature, low density, chemical inertness and low cost. However, in order to use polypropylene In applications such as adheslves, coextrudable tie layers for multilayer composites, metal coatings, and polymer blends, it is necessary to chemically modify polypropylene to incorporate a reactive moiety onto the backbone of the polymer. As a primary advantage of the present invention, one can employ high levels of peroxide and obtain a polymer composition having a high molecular weight with a significant level of functionality which can be made into film or otherwise processed by extrusion, fiber spinning, etc. In contrast, the lower molecular weight functionalized polypropylene produced by conventional approaches generally cannot be so used or processed. A further advantage of the present Invention Is that the molecular weight degradation of polypropylene can be controlled, independent of the level of grafting of maleic anhydride onto the polypropylene, through variation In temperature, time and other process variables. In the prior art, molecular weight degradation

I ncreases when I ncreasi ng amounts of peroxi des are used to increase grafting. The process of this invention does not require the presence of a catalyst, additive, or process modifier (third ingredient) as disclosed 1n U.S. 4,506,056 to prevent molecular weight degradation. The functionalized polypropylene compounds produced with the process of this invention have a melt flow rate (MFR) of one hundred (100) or less, (measured by ASTM Standard F 1238-86), but preferably seventy-five (75) or less. The peroxide Initiators 0 preferred for use in practice of the process have a short 1 half-life t _l/2 at 180 ^* C, preferably less than 3 seconds at ² 180'C, and the peroxide Initiator decomposes to produce radical - fragments 1n combinations of either R ^» or R0», wherein R 1s an ⁴ alkyl group, preferably a C.-C,Q alkyl group. When the ⁵ radical is R0«, R 1s most preferably t-butyl. The energy for - bonding a hydrogen atom to these types of radicals Is about 105 ⁷ Kcal/mol or less. The peroxides preferred for use in the process are t-butyl peroxypivalate or isononanoyl peroxide. ⁹ Brief Description of the Drawings ⁰ Figure 1 1s a graph of the melt flow rate (MFR) versus the ¹ weight percent of maleic anhydride Incorporated for maleated polypropylene compositions produced by using dicu yl peroxide, a typical peroxide used in radical initiated grafting processes, compared to a maleated polypropylene composition produced by either of two preferred embodiments of the process of the present invention, one embodiment being a melt phase process (B) and the second embodiment being a solid phase process (C). Figure 2 is a graph of the melt flow rate (MFR) of a functionalized polypropylene versus the amount of peroxide initiator used to produce the functionalized polypropylene composition, for a functionalized polypropylene produced using dicumyl peroxide in accordance with prior art processes (D) and for a functionalized polypropylene produced using t-butyl peroxypivalate in accordance with the process of this Invention (E). Detailed Description of the Invention The present invention relates to a process for the

funct1onalizat1on, and preferably the maleation of a polyolefin, preferably polypropylene, by use of a selected class of peroxides which will not cause the molecular weight of the polyolefin to significantly degrade. While the differences between polypropylene and its copoly ers are recognized, the term "polypropylene" as used In the claims includes both homopolymers and copolymers of propylene for the sake of convenience. The process of this invention does not require the presence of a catalyst, additive, or process modifier to prevent molecular weight degradation. The functionalizing agent employed in the process of this Invention may be any of the unsaturated monomers conventionally used to functlonalize a polyolefin. Such functlonalizing agents include, for example, carboxylic adds such as acrylic and methacrylic add; acid anhydrides such as maleic and himic anhydride; add amides such as acrylamide; and vinyl slloxanes such as vinyltrimethoxysilane. The functionalizing agent preferred for use in the process shall be described and illustrated with reference to the functionalization of polypropylene by reaction with maleic anhydride (MAH). Although the invention will be described with reference to maleic anhydride, it should be understood that functionalizing reagents different from maleic anhydride, such as the unsaturated monomers previously Identified, can be employed in the practice of this invention. Accordingly, the term "maleation" or "maleated" as used hereafter should be understood to mean "functionalization" insofar as the use of functionalizing reagents other than maleic anhydride are contemplated for use in the process of the invention. The composition resulting from the practice of the process of the Invention is a maleated polypropylene in which the polypropylene has on the average more than 0.3 weight percent (0.13 mole 1) grafted maleic anhydride and preferably greater than o.4 weight percent (0.17 mole 1) grafted maleic anhydride, and an MFR of less than 100. The mole 1 most preferably 1s 1n the range of 0.13-1.71. The melt flow rate (MFR) of the maleated polypropylene, measured by ASTM Standard El238-8, is about one hundred (100) or

* less, preferably less than 75, and most preferably less than 60.

² These values can be compared with the prior art as in Table 2

³ where it is demonstrated that the use of peroxides typically used

⁴ in the prior art produces maleated polypropylenes with MFR's

⁵ greater than 300. Maleated polypropylene made by the prior art

⁶ methods with an MFR of less than 100 contain very low levels of grafted maleic anhydride, as demonstrated by the overlapping area

⁸ of the curves 1n Figure 1 in the region of very low weight percent

⁹ grafted maleic anhydride, low MFR. In accordance with this

-° invention 1n which polypropylene does not significantly degrade, ¹¹ the MFR of the maleated polypropylene product Is related to the ¹ MFR of the initial polypropylene polymer. The advantage of the

13 composition of this Invention 1s that the maleated polymer product 14 can be made Into films or can be processed by extrusion, fiber 15 spinning, etc., and used 1n engineering plastic applications 16 whereas the lower molecular weight functionalized polymers 17 produced by prior art functionalization processes generally have 18 MFR's much greater than 100 and cannot be so processed. 19

In carrying out the process of the present invention, the 20 maleic anhydride and peroxide reagents should be mixed with the 21 polypropylene preferably before the polypropylene is heated, and 2 most preferably the maleic anhydride and the peroxide free radical 3 initiator should be mixed prior to adding such mixture to the 4 polypropylene. Although use of a solvent is not required for 5 mixing the reagents with polypropylene, using an Inert, low 6 molecular weight, volatile solvent, such as pentane, hexane, or 7 other hydrocarbons, or methylethyl ketone, acetone, or other low 8 molecular weight species, or any other suitable liquid, to coat 9 the polymer with the reagents, does improve the ixi.g of the 0 reagents and improve the dispersion of the reagent mixture on the ¹ polypropylene when so used. The mixture of peroxide initiator and ?2 maleic anhydride is added to the polypropylene to coat the polymer 3 with such components of the mixture. If a solvent 1s used as a 4 coating and dispersion aid for the reagents, after the mixture 1s 5 coated onto the polypropylene the solvent is evaporated from the 6 polymer, leaving the maleic anhydride and peroxide reagents on the 7 surface of the polypropylene.

Thereafter, the polymer with the reagents present is treated 1n one of two ways. A preferred mode for conducting the reaction of maleic anhydride with polypropylene is In the melt phase mode wherein the temperature exceeds 160 ^* C. In accordance with this embodiment, a high level of grafting with minimal molecular weight degradation is obtained. In accordance with this mode, the polypropylene 1s mixed with the peroxide and maleic anhydride or coated by evaporation of inert diluent from a slurry of peroxide/maleic anhydride. Typical diluents are pentane, heptane, methyl, ethyl, ketone and the like. Thereafter, the reagent coated polypropylene granules or pellets are heated 1n a vessel such as a Brabender plasticorder, an autoclave, an extruder or other equipment of like purpose or are reacted in a fluldized bed or gas phase reactor. Good results are obtained at temperatures of about 180-250'C, but preferably 180-220*C. The longer the time that the polypropylene Is subjected to the reaction temperature, namely the preferred temperature of 180-220'C, the greater will be the amount of grafted maleic anhydride, without further degrading the molecular weight of the polypropylene. An alternative method for conducting the maleation reaction is in the particulate or solid phase, at a temperature below the melting point of the polypropylene, namely at a temperature of less than about 165 ^* C. In accordance with this mode, the closer to 165'C the better the grafting results obtained. The MFR of maleated polypropylene products produced in the particulate phase is less than fifty (50) but most commonly less than ten (10) when starting with a polypropylene resin having an MFR of 3. The longer the time that the polypropylene is subjected to the reaction temperature, namely the preferred temperature of 150-165 ^* C, the greater will be the amount of the grafted maleic anhydride, without further degrading the molecular weight of the polypropylene. Alternatively, in either the melt phase or solid phase mode, the maleic anhydride and the select peroxide can be added to the polypropylene separately. Addition of the maleic anhydride separately from the peroxide results in lower grafting levels, but

maintains the advantage of insignificant molecular weight degradation of the polymer product. Since 1n the process of the present invention the molecular weight of the polypropylene 1s not significantly degraded, the amount of the peroxide used, based on the quantity of polypropylene to be reacted, may be as high as 10 mole percent, calculated as the number of moles of peroxide per mole of propylene monomer units (- ₃ H, units) present. The preferred amounts of the peroxide Initiator are in the range of about 0.14 to 6 mole percent. The presence of a catalyst, additive, or other process modifier during reaction 1s not required in order to accomplish the objectives of the present Invention, namely, the grafting of substantial quantities of maleic anhydride to polypropylene without significant degradation of the polypropylene molecular weight. However, such catalysts, additives, or other process modifiers can be Included 1n this reaction to obtain similar results as given in the prior art for other processes using other peroxides (EPO Patent Application 0225186). As above mentioned, it 1s generally desirable in this invention to use a minor amount of a low molecular weight hydrocarbon or other solvent to enhance the mixing of the reagents and to disperse the reagent mixture on the polypropylene. With the process of the present invention the maleated polypropylene produced will have an MFR of one hundred (100) or less, i.e., from 0 to 100, and desirably 0-75, and most desirably 0-60, indicating that the molecular weight of the maleated polypropylene product 1s much higher than the prior art polymers of polypropylene with equivalent amounts of maleic anhyαride grafted using peroxide Initiators. Also, in accordance with this Invention the amount of maleic anhydride grafted is greater than 0.3 weight percent and preferably greater than 0.4 weight percent grafted maleic anhydride with an MFR of less than 100 which distinguishes the present invention from the prior art. The preferred peroxide Initiators for use in carrying out the present Invention so as to obtain the results indicated above are t-butyl peroxypivalate and Isononanoyl peroxide. The class of

1 peroxide initiators which are capable of successful use In the

2 present Invention may be more broadly classified as peroxides

3 which have radical fragments when the peroxide Is dissociated,

4 which are a combination of R« and R0«, where R Is an aliphatic

5 hydrocarbon, and 0 is oxygen. Such radical fragments exist (1)

6 when the peroxide separates at the two oxygen atoms 1n the middle

7 of the peroxide (dissociation), or (2) when the fragments formed

8 by dissociation undergo decarboxylatlon or beta-scission after

9 separation at the two oxygen atoms in the middle of the peroxide. 10 The dissociation pathway for t-butyl peroxypivalate is:

U 0

12 II dissociation

13 [13 (CH3) ₃ C-C-0-0-C(CH ₃ )3 > [2]

14 0

1 ₅ || decarboxylatlon

₁₆ C2] (CH ₃ ) ₃ C-C-0» + -0-0(^3)3 >[33

₇ [33 (CH ₃ ) ₃ 0 + C0 ₂ + -0-C(CH ₃ )3 8 R0« 9 It has been found that the hydrogen bond energy, i.e the ₀ energy gained by adding a hydrogen radical (H«) to a peroxide i radical (P«):

2 P« + H« > P-H ΔH « hydrogen bond energy

3 can be related to whether the peroxide initiator will function in ₄ the present invention. Table 1 shows the hydrogen bond energy and ₅ conversely the radical stability for various free radicals or ₆ radical fragments which may exist after a peroxide dissociates.

TABLE 1

Approximate Radical Reactivity

Radical Type Hydrogen Bond Energy (Hydrogen Abstraction)

ctive

R ₃ C 91 Kcal/mol Least Reactive

Peroxides which dissociate into free radicals with a hydrogen bond energy of about 105 Kcal/mol and below, and which have a short half life at 180 ^β C are most satisfactory for the purposes of the present invention, namely, producing a functionalized polypropylene, particularly a maleated polypropylene, with minimal degradation of its molecular weight. EXAMPLES

In the examples and tables which follow, the quantities of reagents employed and the properties of resulting compositions were determined as follows:

The melt flow rate (MFR) of the starting polymer and of the maleated polymer product were determined 1n accordance with ASTM Standard D1238-86, i.e., a melt temperature of 230'C and a load of 2.16 Kg.

The amount of maleic anhydride (MAH) used for reaction with a polymer 1s reported as weight percent MAH. The weight percent MAH was calculated as the number of grams of maleic anhydride present per gram of polymer multiplied by 100.

The molar concentration of peroxide used, as reported in the

1 examples and tables, was calculated as the number of moles of

² peroxide per mole of monomer units 1n the polymer being reacted.

³ Wherein polypropylene was the polymer reacted (Examples 1 to 23) the molar concentration of peroxide used was calculated as the

⁵ ratio of the moles of peroxide to the moles of propylene monomer

⁶ units (C ₃ Hg, M.W. - 42 g/mole) present in the polymer.

⁷ Wherein an ethylene-propylene copolymer was the polymer reacted

⁸ (in Examples 23-27) the molar concentration of peroxide used was

⁹ calculated as the ratio of moles of peroxide to the sum of the -- moles of propylene and ethylene monomer units (C ₃ H _β , M.W. « 42 ¹ g/mole; .H ₄ , M.W. - 28 g/mole) present. ² To determine the amount of maleic anhydride grafted onto the

¹³ polymer, the maleated polymer was dissolved in xylene then

¹⁴ precipitated from solution with acetone, filtered and dried. All

¹⁵ samples in the examples were treated in this fashion. The weight

¹⁶ percent of maleic anhydride grafted to the polymer was then

¹⁷ determined by Fourier Transform Infrared (FTIR) analysis. FTIR

¹⁸ films were pressed at 230'C for several minutes. The maleic

¹⁹ anhydride concentrations grafted to the polymer were calculated

²⁰ from the intensity of the peak appearing between 1782-1790 cm ^" .

²¹ The FTIR was calibrated by oxygen analysis performed on maleated

²² polypropylene and maleated ethylene-propylene rubber samples. The ² molecular weight of the grafted polymer was monitored by measuring

²⁴ the melt flow rate (MFR) using ASTM Standard D1238-86 and by Gel

²⁵ Permeation Chromatography (GPC).

-° The amount of maleic anhydride and peroxide reagents used and

²⁷ their relative concentration, as well as the temperature chosen,

²⁸ the time of reaction, the MFR or molecular weight of the polymer

²⁹ starting material, ai.d the method of addition of the reagents to

³⁰ the polymer starting material were chosen to illustrate the

³ - variety of desired results that may be achieved by varying such

³² conditions in the practice of the process of this invention. The

³³ examples which follow are illustrative of such variations, but are

³⁴ not intended to limit or otherwise exclude other combinations of

³⁵ such parameters.

³⁶ Specific examples of peroxide initiators which are

³⁷ unsatisfactory and those which are satisfactory in carrying out

the present Invention are given below as Examples 1-11 (comparative) and Examples 12-13 (Inventive). Table 2, following Example 13, shows data obtained for the various peroxide Initiators utilized in Examples 1-13. Examples labelled with a "C" are comparative examples. Example 1-C The reaction of isotactic polypropylene having a melt flow rate (MFR) of 3.0 and maleic anhydride in the presence of a peroxide initiator was carried out In a Brabender plasticorder. One hundred forty-four milligrams (144 g) of dicumyl peroxide (0.07 mole percent) was mixed with 1.6 g maleic anhydride (5 weight percent) at room temperature in the powder form and then mixed with 32 grams of polypropylene granules. The Brabender plasticorder was brought to a temperature of 180'C and rotated at 30 rpm. While rotating at 30 rpm, the powdered peroxlde-maleic anhydride-polypropylene mixture was added to the Brabender plasticorder after which the speed of the Brabender was increased to 60 rpm. The polymer mixture was blended for 10 minutes at 180'C, then removed from the Brabender. The results are summarized in Table 2. Example 2-C The procedure of Example 1 was followed except that 0.14 mole percent dicumyl peroxide (288) mg was used. The results are summarized in Table 2. Example 3-C The procedure of Example 1 was followed except that 0.24 mole percent dicumyl peroxide (0.48 g) was used. The results are summarized in Table 2. Example 4-C The procedure of Example 1 was followed except that 0.31 mole percent dicumyl peroxide (0.64 g) was used. The results are summarized 1n Table 2. Example 5-C The procedure of Example 1 was followed except that 0.47 mole percent dicumyl peroxide (0.96 g) was used. The results are summarized in Table 2.

Example 6-C The procedure of Example 1 was followed except that 0.62 mole percent dicumyl peroxide (1.3 g) was used. The results are summarized in Table 2. Example 7-C The procedure of Example 1 was followed except that 0.78 mole percent dicumyl peroxide (1.6 g) was used. The results are summarized in Table 2. Example 8-C The procedure of Example 1 was followed except that 4.05 grams of dicumyl peroxide (1.75 mole percent) 3.6 grams of maleic anhydride (10 weight percent MAH) and 36 grams of polypropylene were used. The results are summarized 1n Table 2. Example 9-C The reaction of Isotactlc polypropylene having a MFR of 3.0 and maleic anhydride in the presence of a peroxide Initiator was carried out in a Brabender plasticorder. Maleic anhydride, 10 weight percent, and 2,5-dimethyl-2,-5-di(t-butylperoxy) hexane (tradename Lupersol 101), 1.75 mole percent, were dissolved in methyl ethylketone at ambient temperature, then mixed with 36 g polypropylene granules. The solvent was then evaporated from the mixture to leave the peroxide and MAH reagents on the surface of the polypropylene granules. A brabender plasticorder was brought to a temperature of 180'C and rotated at 30 rpm. While rotating at 30 rpm, the peroxide-maleic anhydride-polypropylene mixture was added to the Brabender plasticorder after which the speed of the Brabender was increased to 60 rpm. The polymer mixture was blended for 10 minutes at 180'C, then removed from the Brabender. The results are summarized in Table 2. Example 10-C The procedure of Example 9 was followed except that 1.75 mole percent of t-butyl peracetate (3.6 g) was used as the peroxide Initiator. The results are summarized in Table 2. Example 11-C The procedure of Example 9 was followed except that 1.75 mole percent of benzoyl peroxide (3.9 g) was used as the peroxide initiator. The results are summarized 1n Table 2.

Example 12 The procedure of Example 9 was followed except that 1.61 mole percent of isononanoyl peroxide (7.2 g) was used as the peroxide initiator and 20 weight percent MAH was used. The polymer mixture was blended for five minutes at 210'C. The results are summarized in Table 2. Example 13 The procedure of Example 9 was followed except that 1.75 mole percent of t-butyl peroxypivalate (3.6 g) was used as the peroxide initiator. The results are summarized in Table 2.

Table 2.

•isoPP = isotactic polypropylene

¹ Table 2 vividly illustrates that the MFR of the polymers

² maleated in accordance with the preferred process of this

³ invention using preferred peroxide initiators, such as t-butyl

4 peroxypivalate and isononanoyl peroxide are well below one hundred

⁵ (100) demonstrating that minimal molecular weight degradation

⁶ occurs with peroxide initiators which satisfy the criteria set

⁷ forth for use in this Invention, while still grafting significant amounts of maleic anhydride.

⁹ As Illustrated by the contrast of Examples 12 and 13 with -° Examples 1-11, it 1s also important to the process of this Invention that the peroxide initiators have a relatively short

¹² half-life at 180'C. The half-life values Identified 1n Table 2 ³ for each peroxide were calculated using activation energies and

¹⁴ rate constant data from the Polymer Handbook. 2nd Edition, - Brandrup & Immergut. The two preferred peroxide Initiators, for - example, have a half-life of tenths of a second at 180'C. Once ⁷ chosen, the peroxide Initiators, with a half-Hfe of less than 8 about three seconds at 180'C, can be used at any temperature. A ⁹ peroxide having a half-life of over a few seconds at 180'C will ⁰ produce a maleated polypropylene product which has a significantly reduced molecular weight. 2 The following examples Nos. 14-22 illustrate the melt phase 3 mode of maleation of polypropylene 1n accordance with the process 4 of this invention. 5 Example 14 6 T-butyl peroxypivalate as the peroxide initiator, maleic anhydride, and polypropylene pellets (MFR « 1.0) were added ⁸ directly to the feed hopper of a single screw extruder-reactor and ⁹ then passed into the feed zone of the extruder. The polymer ⁰ passed through all zones of the reactor, held at 180'C, with an 1 average residence time of 1.5 minutes. The amount of peroxide and ² maleic anhydride used, and the product MFR and MAH grafting level ³ are shown in Table 3. ⁴ Examples 15-21 ⁵ T-butyl peroxypivalate as the peroxide Initiator and maleic ⁶ anhydride were dissolved 1n methyl ethylketone at ambient ⁷ temperature, then mixed with polypropylene granules, MFR 3.0. The

solvent was evaporated leaving the MAH and peroxide on the surface of the polymer. A Brabender plasticorder was brought to a temperature of 180'C and rotated at 30 rpm. While rotating at 30 rpm the peroxide-maleic anhydride-polypropylene mixture was added to the Brabender plasticorder after which the speed of the Brabender was increased to 60 rpm. The polymer mixture was blended for 10 minutes at 180'C, then removed from the Brabender. The amount of peroxide and maleic anhydride used and the time of reaction varied and is reported for each example in Table 3 which follows. Example 22 The procedure of Example 20 was followed except that the Brabender plasticorder was brought to a reaction temperature of 200'C and the peroxide-MAH-polymer mixture was blended for only 2 minutes. The results are reported in Table 3. The following examples Nos. 23-25 illustrate the solid phase mode for maleation of polypropylene in accordance with the process of this invention. Examples 23-25 Maleic anhydride and t-butyl peroxypivalate (TBPP) as the peroxide initiator were dissolved in methyl ethylketone at ambient temperature, then mixed with polypropylene granules, MFR 3.0. The solvent was evaporated leaving the MAH and peroxide on the surface and in the pores of the polymer granules. The dry mixture of peroxide-MAH-polypropylene was added to an autoclave and the autoclave was purged with nitrogen for 15 minutes. The autoclave

_3 was evacuated to 10 torr and then closed to external atmosphere. The autoclave was then heated to 150'C and stirred for a period of time after which its temperature was reduced to room temperature and it was returned to atmospheric pressure. The amount of peroxide and maleic anhydride used and the temperature and time of reaction for each example are summarized in Table 3.

Table 3.

* JsoPP - otactk polypropylene ** TBPP - t-butyl peroxyplvjlite

Table 3 demonstrates that parameters such as temperature, reaction time, apparatus type, and reagent concentration can be varied to control the level of grafting and molecular weight breakdown during PP functionalization. In particular it should be noted that when an enclosed apparatus such as an extruder is used (Example 14) a much lower quantity of reagents 1s required to obtain similar grafting results to the Brabender, which is open at the top.

The polymers useful in this invention include polypropylene and random or block copolymers of propylene with a lesser amount -- of one or more C ₂ -C ₁₈ ) α-olefins and/or diolefins such as - ethylene, butene, hexene, butadiene, hexadiene, and so on. Use of

¹³ such copolymers results in even higher grafting levels and lower

¹⁴ MFR levels than are achieved in the case of homopolypropylene.

¹⁵ The lower MFR is achieved because, in addition to the elimination

¹⁶ of molecular weight breakdown as described by this invention, some

¹⁷ crosslinking occurs in the presence of a peroxide in a copolymer - ⁸ containing other olefins, such as ethylene. This crosslinking - phenomenon is well known in the art. Example Nos. 26-32

²⁰ illustrate the application of this invention to copolymers of propylene with ethylene. The results of such examples are shown

²² in Table 4.

23 Examples 26 through 29 illustrate melt phase maleation of 24 ethylene-propylene copolymers using the process of this 25 invention. Example 30 illustrates melt phase maleation of 26 ethylene-propylene using prior art. The results are summarized in 27 Table 4. 28 Example 26

²⁹ An ethylene-propylene copolymer containing 3 weight percent ethylene was maleated in accordance with the process of the

³¹ invention. Maleic anhydride and t-butyl peroxypivalate (TBPP) as

32 the peroxide initiator were dissolved 1n methyl ethylketone or 33 pentane at ambient temperature, then mixed with polypropylene

³⁴ granules, MFR 3.0. The solvent was evaporated leaving the MAH and

³⁵ peroxide on the surface and in the pores of the polymer granules.

³⁶ A Brabender plasticorder was brought to a temperature of 180'C and

³⁷ rotated at 30 rpm. While rotating at 30 rpm the peroxide-maleic

anhydride-polypropylene mixture was added to the Brabender

² plasticorder after which the speed of the Brabender was Increased

³ to 60 rpm. The polymer mixture was blended for 10 minutes at

⁴ 180'C, then removed from the Brabender.

⁵ Example 27

- The procedure of Example 26 was followed except that the ethylene-propylene copolymer used contained 5 weight percent ethylene.

⁹ Example 28

1- The process and procedure of Example 14 (extruder reactor) was

11 followed except that the polymer used was an ethylene-propylene 2 copolymer. 3 Example 29 ⁴ The process and procedure of Example 28 was followed except ⁵ that the temperatures 1n the last 2 segments of the extruder were - raised to 200'C and 220'C respectively. ⁷ Example 30-C ⁸ The process and procedure of Example 14 (extruder reactor) was ⁹ followed except that the polymer used was an ethylene-propylene ⁰ copolymer and the peroxide used was a 2,5- i ethyl-2,5-di ⁱ (t-butylperoxy)hexene (tradename Lupersol 130). The results are ² summarized in Table 4. ³ Examples 31 and 32 Illustrate the solid phase maleation of ethylene-propylene copolymers using the process of this invention. ⁵ Example 31 ⁶ An ethylene-propylene copolymer containing 3 weight percent ⁷ ethylene was maleated in accordance with the process of the ⁸ Invention. Maleic anhydride and t-butyl peroxypivalate as the ⁹ peroxide initiator were dissolved In methyl ethylketone or pentane ⁰ at ambient temperature, then mixed with polypropylene granules, ¹ MFR 3.0. The solvent was evaporated leaving the MAH and peroxide ² on the surface and 1n the pores of the polymer granules. The dry ³ mixture of peroxide-MAH-polypropylene was added to an autoclave ⁴ and the autoclave was purged with nitrogen for 15 minutes. The ⁵ autoclave was evacuated to 10 Torr and then heated to 150'C. ⁶ The contents were stirred for 60 minutes. ⁷ Example 32

Table 4.

* isoPP = isoiactic polypropyslene »« -T-jpp ₌ t-but l peroxypivalate

1 The procedure of Example 26 was followed except that the

² ethylene-propylene copolymer used contained 5 weight percent

³ ethylene. The results are summarized in Table 4.

⁴ Examples 31 and 32, conducted at 150'C show that significantly

⁵ less molecular weight degradation occurs In the solid phase - experiment than 1n the melt phase experiment. Comparison of

⁷ Examples 26-28 with the previous examples demonstrates that the

⁸ crosslinking affect achieved with the presence of ethylene monomeric units in the polypropylene polymer results in slightly 1° lower MFR than when the crosslinking ability is not present

H (homopolypropylene). Concomitantly, the 5 percent ethylene copolymer exhibits the lowest MFR under the same maleation

1 ³ conditions.

1 ⁴ The foregoing disclosure and description of the invention are

15 Illustrative and explanatory thereof, and various changes In the 1- size, shape and materials, as well as in the details of the

I ⁷ Illustrated construction may be made without departing from the lδ spirit of the invention.