JP2015028180A - Maleated polypropylenes and processes for preparation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide maleated polypropylenes having a relatively high percentage of bound maleic anhydride, based on the total amount of maleic anhydride moieties present in a grafting reaction product.SOLUTION: Maleic anhydride is introduced to a polypropylene, and preferably a polypropylene melt, at a rate that maintains the concentration of maleic anhydride in the reaction mixture (e.g., in the melt) at about 120% or less, and preferably 100% or less, of the solubility limit of the maleic anhydride in the polypropylene at the reaction conditions. Thereby, a maleated polypropylene is produced in which at least about 60% of the maleic anhydride moieties in the grafting reaction product are bound to the polypropylene.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is related to and claims the priority benefit of US Provisional Patent Application No. 60/289269, filed May 6, 2001. The provisional patent application is assigned to the assignee of the present invention and is hereby incorporated by reference.

FIELD OF THE INVENTION The present invention relates to maleated polypropylene and a method for producing maleated polypropylene. More particularly, the present invention relates to a process for producing maleated polypropylene having a relatively high percentage of bound maleic anhydride moieties and to the maleated polypropylene obtained from such a process.

Maleated polyolefins, particularly maleated polypropylene, are known in the art and find use in a wide range of applications. For example, maleated polypropylene is useful for compatibilizing polymers, particularly polyolefins, with various polar substrates including polar polymers, inorganic fillers, and the like. Such copolymers are also known for use in metal bonded adhesive compositions.

Many classes of techniques are known for grafting maleic anhydride onto the polymer backbone. For example, maleation in the solid state occurs below the melting point of the polymer and the reaction occurs at the exposed surface of the polymer. In solvent-based grafting, the substrate polymer is dissolved in a suitable solvent and the grafting reaction occurs in solution. In melt grafting, maleic anhydride is grafted onto the polypropylene backbone by introducing maleic anhydride or a precursor thereof into the polypropylene polymer melt, typically in the presence of a catalyst.

Applicants have found that the conditions typically used so far for grafting maleic anhydride onto the polymer backbone, in particular those that typically occur in melt grafting, are undesirably a small percentage of maleic anhydride. It has been found that the acid tends to result in bonding to the polymer backbone. More particularly, Applicants have described, for example, US Pat. No. 3,642,642.
722- Knowles et al. And 45006056-Gaylord (
Each of these is prior art methods such as those disclosed in US Pat. No. 6,057,086, wherein less than about 50% of the maleic anhydride in the graft reaction product is bound to the polypropylene backbone. Has been found to result in a maleated polypropylene product. Applicants have determined that the remainder of the maleic anhydride present in the prior art graft reaction product is the same as Scott M., one of the co-inventors herein. Hacker's “Not All Mal
It is considered to be unreacted and / or oligomeric maleic anhydride, as shown in a paper / study entitled “eated Polyolefins Are Created Equal”, which is appended hereto.

Applicants have recognized that not only the above disadvantages of the prior art, but these disadvantages result in products having insufficient performance characteristics in certain applications. More particularly, Applicants have noted that one important use for maleated polypropylene is compatibilizers, specifically polar substrates,
It has been found that it is as a compatibilizer for fibers and fillers. Applicants understand that as the level of bound maleic anhydride increases, the compatibility properties of the product increase. Bound maleic anhydride provides the desirable properties of maleated polypropylene,
Unreacted and oligomeric maleic anhydride present in the product tends to suppress such properties. Indeed, unbound maleic anhydride compounds remaining in the maleated polypropylene product act as scavengers and tend to suppress the compatibility properties of maleated polypropylene.

The present invention relates to a process for advantageously producing maleated polypropylene having a relatively high percentage of bound maleic anhydride based on the total amount of maleic anhydride moieties present in the graft reaction product, and the maleate produced therefrom. Targets fluorinated polypropylene. The method of the present invention requires at least about 60% of the maleic anhydride moiety in the graft reaction product.
Overcoming the disadvantages of the prior art by promoting the formation of maleated polypropylene, preferably at least about 75% bonded to polypropylene. In this specification, unless otherwise specified, all percentages refer to weight percent.

The improved method carefully selects the type and nature of the reactants used, and the maleic anhydride is added to the selected polypropylene, preferably polypropylene melt, at least about 55% of maleic anhydride, and even more preferably at least about 60% is added under conditions of temperature and pressure for a period effective to graft to the polymer backbone, wherein said percentage is the total maleic anhydride moiety present in the grafting reaction product (precursor thereof). Including body).

As used herein, the term “graft reaction product” refers to maleated polypropylene as well as any unreacted components, by-products after the grafting reaction is deemed substantially complete, but prior to any subsequent purification steps. Refers to products and impurities. As used herein, the term “polypropylene” refers to polypropylene homopolymers and all forms of polypropylene copolymers, especially polypropylene-polyethylene, where at least approximately the majority of the polymer is formed on a mole percent basis. Including and including copolymers. As used herein, the term copolymer refers to and includes terpolymers and the like. Preferably, the polyolefin reactant of the present invention is a polypropylene homopolymer or a copolymer of propylene and ethylene having a weight based concentration of ethylene of less than about 10%, more preferably less than about 5%. As used herein, the term “maleated polypropylene” generally refers to a reaction product formed by grafting maleic anhydride onto a polypropylene polymer backbone, preferably covalently. Thus, as is known in the art, such graft reaction products in commercial applications are generally
Not only maleated polypropylene but also unbonded maleic anhydride and oligomeric maleic anhydride. As used herein, the term “bound maleic anhydride” generally refers to a moiety derived from maleic anhydride that is grafted to a polypropylene backbone in accordance with the present invention. “Unbound maleic anhydride” generally refers to unreacted maleic anhydride or oligomeric anhydride present in the graft reaction product. In embodiments where the reaction occurs in the molten state, the graft reaction product is generally a melt at the end of the graft reaction step.

In certain preferred embodiments, maleic anhydride is added to the polypropylene, preferably polypropylene melt, the concentration of maleic anhydride in the reaction mixture (eg, in the melt), and the solubility limit of maleic anhydride in polypropylene at the reaction conditions. Of about 120% or less, more preferably 100% or less.

Applicants have grafted maleic anhydride onto polypropylene in a reaction mixture in which the amount of unreacted maleic anhydride in the mixture is maintained at a relatively low level, resulting in very high levels of bound maleic anhydride. It has been unexpectedly and counter-intuitively discovered that it can result in reaction product copolymers containing and / or containing relatively low levels of oligomeric maleic anhydride.

In embodiments where the reactant comprises a polypropylene-polyethylene copolymer, Applicants have also unexpectedly discovered that the amount of maleic anhydride bound in the grafting reaction is generally related to the amount of polyethylene in the copolymer. did. More particularly, the copolymer comprises no more than about 10 mol% polyethylene, more preferably no more than about 5 mol% polyethylene, and even more preferably about 0.5 mol% to about 3 mol% polyethylene. But,
Generally preferred. Applicants help polyethylene levels as described herein produce the claimed high levels of bound maleic anhydride without adversely affecting the compatibility properties of the reaction product. I discovered that.

Thus, the present invention provides a polypropylene backbone, bound maleic anhydride, and about 0%
An improved maleic anhydride / polypropylene graft copolymer product comprising about 40% unbound maleic anhydride, based on the total maleic anhydride moieties in the reaction product, at least about 60% by weight Wherein said maleic anhydride moiety, more preferably at least about 65% by weight of said maleic anhydride moiety, even more preferably at least about 70% of said moiety is bound maleic anhydride. . In a particularly preferred embodiment, at least about 75% of said moiety is bound maleic anhydride, based on the total maleic anhydride moiety in the reaction product.

FIG. 3 is a graph showing the percentage of bound maleic anhydride plotted against SAP for low and high molecular weight polypropylene.

DESCRIPTION OF THE PREFERRED EMBODIMENTS One aspect of the present invention is directed to a method for producing maleated polypropylene comprising reacting maleic anhydride or precursor thereof with polypropylene in a reaction mixture.
A wide range of known methods and steps for combining and reacting maleic anhydride and polypropylene in the reaction mixture can be adapted to various specific process and unit parameters for use in this reaction step. Can be used according to. For example, the process of the present invention can comprise one or more classes of reaction procedures known in the art, such as melt grafting, solid state grafting, solution grafting, and the like.
However, the present invention is preferably practiced by melt grafting.

The process of the present invention can be performed on a continuous basis, a batch basis, or a combination of both. Those skilled in the art will be able to employ any of these modes of operation in the present invention without undue experimentation in light of the teachings contained herein.

The amount of maleic anhydride bound in the reaction process of the present invention can be affected by a number of reaction parameters including the properties of polypropylene as described above, and applicants have found that high levels of bound maleic anhydride In order to achieve low levels of unreacted and oligomeric maleic anhydride, and / or to achieve low levels of unreacted maleic anhydride, it would be highly advantageous to control one or more relevant parameters in accordance with the teachings of the present invention. In general, the graft reaction step of the present invention can be carried out under any combination of specific graft reaction conditions, provided that the reaction of polypropylene and maleic anhydride is either maleic anhydride and itself or a reaction mixture. The condition is that it is promoted compared to the reaction with other components in it, such as maleic anhydride oligomer.

One of the preferred mechanisms for obtaining the reaction mixture, which greatly promotes the polypropylene / maleic anhydride grafting reaction, uses the unreacted maleic anhydride concentration in the reaction mixture in the prior art process. It is to maintain a relatively low level compared to the level. Although Applicants do not seek to be bound by or to any operational theory, an unexpectedly high percentage of bound maleic anhydride found in the preferred product of the present process is at least partially because maleic anhydride is in polypropylene. More particularly, it is conceivable to achieve due to having limited solubility in the polypropylene polymer melt. Therefore, the use of low concentrations of maleic anhydride results in less phase separation of maleic anhydride or its precursor and polypropylene in the reaction mixture. Thus, the use of maleic anhydride concentrations that do not substantially exceed the solubility limit of the polymer has two distinct beneficial results. First, it results in a very high percentage of maleic anhydride being in the same phase as and in intimate contact with the polymer molecule, which is preferred for anhydride / polymer reactions. Second, the present invention minimizes the amount of unreacted maleic anhydride that is exposed to conditions that promote the anhydride / anhydride reaction as occurs with maleic anhydride present in the phase away from the polymer phase. Can be suppressed. Thus, less phase separation allows a higher percentage of maleic anhydride to be introduced into the polymer melt.
Further, the initially formed and lightly maleated product is believed to help solubilize any additional maleic anhydride reactant that is subsequently introduced into the polymer melt in a preferred embodiment of the present invention.

Certain preferred embodiments, particularly from about 200 cps at 190 ° C. to about 2000 cps at 190 ° C.
In accordance with an embodiment involving the production of a grafted polypropylene copolymer having a viscosity of The acid concentration is less than about 2.5%, more preferably about 2
Reacting maleic anhydride with polypropylene under conditions effective to maintain less than 1%, even more preferably less than about 1%. In certain embodiments, the graft reaction step is performed during a substantial portion of the addition step, preferably at least about 75%.
Under conditions effective to maintain the maleic anhydride concentration in the reaction mixture at a weight percent of less than about 2.5, more preferably less than about 2%, and even more preferably less than about 1%, Adding to a reaction mixture comprising polypropylene, preferably a polypropylene melt.

The term “substantial portion” as used herein with respect to the reaction step and the addition step refers to any portion or portions of the graft reaction in which at least 50% of the maleic anhydride-polypropylene bond is formed overall. .

In certain embodiments where the reaction is a batch reaction, maleic anhydride is a rate of less than about 0.045 pounds of maleic anhydride or precursor thereof ("MA") per pound of polypropylene ("PP") per hour. The graft reaction conditions (MA / PP / hr), even more preferably less than about 0.040 MA / PP / hr, are preferably added to the reaction mixture.

In addition to this, Applicants find in the final product the molecular weight of the polypropylene used in the maleation process, as well as the maleic anhydride content of the maleated polypropylene, typically characterized by the saponification number of the final product. It was found to affect the percentage of maleic anhydride bound. As used herein, the term saponification number (“SAP”) refers to a saponifiable material present in maleated polypropylene, such as bound single unit maleic anhydride, bound oligomeric maleic anhydride, A measure of the amount of reacted maleic anhydride, unbound oligomeric maleic anhydride, and other hydrolyzable moieties. SAP is generally calculated as the number of milligrams of potassium hydroxide (mg KOH / g) required to hydrolyze a 1 gram sample. FIG. 1 is a graph depicting the percentage of bound maleic anhydride plotted against SAP for low and high molecular weight polypropylene. As illustrated in FIG. 1, in general, the percentage of maleic anhydride bound decreases with increasing SAP. In addition, as the molecular weight of polypropylene increases, the percentage of what is bound decreases. Controlling such variables in accordance with the present invention is believed to produce useful maleated polypropylene having a high percentage of bound maleic anhydride. More particularly, it is preferred to select the molecular weight of the polypropylene reactant and the SAP of the reactant to achieve a bound maleic anhydride according to the present invention. For embodiments using high molecular weight polypropylene as terminology used by those skilled in the art, the high molecular weight polypropylene does not exceed about 70, more preferably does not exceed about 75.
Even more preferably, it has an SAP not exceeding 80. For embodiments using low molecular weight polypropylene as terminology used by those skilled in the art, the polypropylene does not exceed about 100, more preferably does not exceed about 120, even more preferably 15
It is preferred to have an SAP that does not exceed zero.

Any commercial grade maleic anhydride or precursor thereof, such as maleic acid, which is converted to maleic anhydride under many commonly used grafting reaction conditions,
Suitable for use in the present invention. Examples of suitable maleic anhydride include, for example, Monsant
o Male Anhydride by Company (St. Louis, NO)
commercially available as e, and Huntsman Petrochemical
Manburi Ma by Corporation (Chesterfield, MO)
Those commercially available as leic Anhydride are included.

Polypropylenes suitable for use in the present invention include, for example, Honeywell (Morrr
for example, polypropylene sold under the name ACX1089 by Istown, NJ).

Any suitable amount of maleic anhydride and polypropylene can be used in the methods herein. In certain preferred embodiments, the weight ratio of polypropylene to maleic anhydride used in the process is from about 5: 1 to about 40: 1. More preferably, the weight ratio is about 5: 1.
To about 25: 1, even more preferably from about 10: 1 to about 20: 1.

In certain preferred embodiments of the present invention, the reaction step further comprises reacting maleic anhydride with polypropylene in the presence of a catalyst. Any wide range of catalysts can be used in the present invention. Suitable catalysts are, for example, known in the art and include, for example, dialkyl peroxides, tert-butyl hydroperoxide, cumene hydroperoxide, p-menthane peroxide, p-menthane hydroperoxide, or azobis (isobutyronitrile). Free radical formers including axo compounds, or radiation sources. The preferred free radical source is peroxide, more preferably butyl peroxide. The most preferred peroxide is ditertiary butyl peroxide (di-tert-butyl peroxide) because it is readily available and the results obtained are appropriate and good. These compounds are for example Elf
Lupersol 101 or Di-t-Butyl Per by Atochem
as an oxid, and Akzo Nobel Chemicals Inc. Is commercially available as Trigonox B.

The amount of peroxide or free radical used is generally very small and is about 0. 0, based on the starting material.
It is on the order of 01 to about 5 wt%, preferably about 0.1 to about 3 wt%, with about 0.75 to about 1.25 wt% being most preferred. An amount well above 5% by weight is not necessary for good properties, and an amount below about 0.01% by weight results in an incomplete reaction that is too slow.

As with the polycarboxylic acid compound feed, it is highly preferred to gradually add free radical initiator to the bulk reactant. Free radical initiator is added to the reactants, preferably about 0.01 per hour.
To about 3 wt% starting material, more preferably at a rate of about 0.1 to about 1 wt% starting material per hour, even more preferably about 0.3 wt% starting material per hour.

According to certain embodiments, a catalyst is added to the reaction mixture of the present invention. The catalyst can be added simultaneously and / or separately with respect to maleic anhydride. In a preferred embodiment, maleic anhydride and the catalyst are added to the reaction mixture substantially simultaneously in terms of time, but separately in the sense of where they are added to the reaction mixture. That is, maleic anhydride and catalyst are added to the reaction mixture over different periods of time but through different nozzles or inlets that introduce the catalyst at a location displaced from the location of maleic anhydride introduction.

The process of the present invention further comprises the use of other additives in the reaction mixture and / or the final product. In general, any additive that does not substantially interfere with the formation of the product of the invention,
Appropriate amounts may be used. Examples of suitable additives include comonomers such as styrene, chain transfer agents, stabilizers and the like.

The reaction of the present invention can be carried out under any suitable reaction conditions. In general, it is preferred that the polypropylene comprises a polypropylene melt. Thus, it is generally preferred that the reaction temperature be higher than the melting temperature of polypropylene, but preferably less than about 200 ° C. The temperature depends on the particular polypropylene, the free radical initiator / catalyst, and other parameters that affect the grafting reaction rate. At temperatures well below about 150 ° C,
Many of the preferred starting materials are not in molten form and therefore do not react properly with maleic anhydride. However, at temperatures above about 200 ° C., the ease of emulsification and the melt viscosity of the resulting emulsible polyolefin wax are not as high as desired. Accordingly, the reaction temperature is generally preferably about 150 to about 200 ° C, preferably about 180 to about 190 ° C.

The reaction pressure depends inter alia on the reaction temperature and the desired reaction rate. In general, the reaction is preferably carried out under a pressure of about 0 to about 50 psig, more preferably about 5 to about 30 psig, and even more preferably about 10 to about 20 psig. For reactions carried out at or near atmospheric pressure, expensive high pressure equipment is avoided.

In general, the grafting reaction of the present invention is carried out such that at least about 60% by weight of maleic anhydride, based on the total weight of maleic anhydride in the graft reaction product, is attached to the polymer backbone. Preferably, the reaction is carried out so that at least 70% by weight of maleic anhydride is bound, even more preferably at least 80% by weight.

EXAMPLES Comparative Example This example illustrates the production of maleated propylene according to the prior art as represented in US Pat. No. 3,642,722.

High molecular weight polypropylene having an inherent viscosity of 1.5 is fed to the pyrolysis unit over an average contact time of 30 minutes. Pyrolyzer 370
The operation is carried out using a stirrer operated at a temperature such that all of the thermal energy for decomposition is supplied by mixing friction at a temperature of 0C. Decomposed polypropylene wax is 190 ° C
Having a melt viscosity of about 800 centipoise as measured by When this material is passed through a thermally stirred reactor maintained at about 200 ° C. with 5 wt% maleic anhydride and 0.25 wt% ditert-butyl peroxide, the reaction product A mixture is formed, which has a bound maleic anhydride concentration of less than about 50%, even after standard techniques for separating unreacted maleic hydride from the reaction mixture. It was.

Example 1
A clean and dry reactor purged with nitrogen is charged with 89 parts by weight (pbw) of polypropylene (
Hiwax NP055). After the polypropylene is heated and melted and stirring of the polypropylene is started, the temperature is adjusted to 185 to 187 ° C. Nitrogen was interrupted and 9 pbw maleic anhydride was added to the reactor at a rate of 0.034 lbs maleic anhydride / lbs polypropylene / hr and 1 pbw Lupersol and 1 pbw Parol 10
A mixture of 2 pbw peroxide comprising 0 was charged at a rate of 0.008 lbs / lbs polypropylene / hr. The introduction of maleic anhydride and catalyst was started substantially simultaneously, but with the moved reactor inlet nozzle.

After complete addition of the peroxide mixture (occurs 15 minutes after the maleic anhydride addition is complete), the reaction mixture is stirred for an additional 10 minutes. Standard techniques are used in an effort to remove unreacted maleic anhydride. More specifically, a 25 "Hg vacuum is applied to the graft reaction product, and samples are taken periodically to test for unreacted maleic anhydride.
When the vacuum is turned off and the reaction mixture is cooled to 170 ° C., the mixture of graft reaction products after standard vacuum purification is greater than 70%, more preferably greater than about 80%, even more preferably greater than 85% binding. Maleic anhydride.

Aspects of the Invention An improved graft copolymer product comprising a polypropylene backbone, bound maleic anhydride, and about 0% to about 40% unbound maleic anhydride,
The graft copolymer product characterized by the product, the improvement having at least about 60% by weight of the maleic anhydride moiety in the state of bound maleic anhydride.

2. The unbound maleic anhydride comprises unreacted maleic anhydride and unbound oligomers containing maleic anhydride moieties. An improved graft copolymer product as described in 1.

3. An improved method for producing a maleated polypropylene product by grafting maleic anhydride onto polypropylene in a melt reaction, the improvement comprising bonded and unbonded maleic anhydride in the graft reaction product Adding maleic anhydride to the melt at a rate and under conditions effective to produce a graft reaction product comprising at least about 50% by weight of bound maleic anhydride, based on the total weight of the acid. Said method.

4). A method for producing maleated polypropylene, wherein at least about 60% by weight of the maleic anhydride moiety in the reaction product is based on the total weight of bound and unbound maleic anhydride in the reaction product. In a reaction mixture comprising maleic anhydride at a concentration maintained to produce a reaction product, which is bound maleic anhydride,
Said process comprising reacting maleic anhydride with polypropylene.

Claims (1)

An improved graft copolymer product comprising a polypropylene backbone, bound maleic anhydride, and from about 0% to about 40% unbonded maleic anhydride, the modification comprising the maleic anhydride moiety The graft copolymer product characterized by the product having at least about 60% by weight of conjugated maleic anhydride.

Images