Elastomeric polybutylene polymer

This invention generally relates to novel polymers of 1-butene. More particularly, this invention relates to elastomeric polybutylene-1 polymers.

Thermoplastic, predominantly isotactic homo- and copolymers of 1-butene, commonly referred to as poly-1-butene or polybutylene (conventional polybutene-1) are known in the art. Elastomeric polymers including elastomeric polybutylene-1 are also known in the art. In certain applications, there has been an effort to replace conventional polybutylene-1 with elastomeric polybutylene-1. These applications include film sheets and packaging film where the elastic nature of the elastomeric polybutylene-1 is preferred.

Packaging films are required to have certain characteristics which are desirable for the particular application. For example, films which are used for wrapping food such as vegetables, meat or fish, are minimally required to have a good puncture resistance and a good elastic recovery, sometimes also referred to as memory. A good puncture resistance is particularly important when packaging meat with bones because of the greater likelihood of the bones puncturing the film. Good recovery properties are particularly important in packaging food. Usually, the food is sold in service or convenience stores, or in grocery stores where many customers touch the packages. These touchings deform the film, and without the ability to sufficiently recover, the packaged food looks unfresh and often cannot be sold anymore.

It is an object of the invention to provide an elastomeric polybutylene-1 having significantly improved properties.

It is a further object of the invention to provide an elastomeric polybutylene-1 having a significant amount of syndiotacticity.

Accordingly, it is now provided an elastomeric polybutylene-1 having and exhibiting syndiotacticity of greater than ten (10) percent.

The inventive elastomeric polybutylene-1 can be blended with compatible materials such as polypropylene and its copolymers, ethylene-propylene block copolymers, butyl rubbers, and polyisobutylene into a composition having soft and improved elastic properties. Such compositions are particularly suitable in films, hot melt adhesives, textile and fiber applications.

The novel elastomeric polybutylene-1 can also be blended with incompatible materials such as ethylenically unsaturated esters (EVA, EMA, EMAA, EEA), polyester, nylon, polystyrene, styrene block copolymers (SEBS, SIS, SBS) and polyethylenes. Such blends are particularly useful in easy-open packaging and foam applications and in PVC replacement. When oriented, films made of such blends are used as soft and elastic shrink films.

The novel elastomeric polybutylene-1 can also be blended with both incompatible and compatible materials wherein such materials are as previously disclosed.

The inventive elastomeric polybutylene-1 composition also has utility in automotive and hot melt adhesive applications, and in the manufacturing of disposable products.

Polybutylene polymers are well known in the art. These polymers can be homopolymers or copolymers. The homopolymers of polybutylene can be further classified into isotactic, atactic, or syndiotactic. Conventional polybutylene is predominantly isotactic and has a high degree of crystallinity. Prominently useful properties of conventional isotactic polybutylene include toughness, resistance to creep, and resistance to environmental stress cracking. These properties enable conventional isotactic polybutylene to be useful in applications such as pipe or tubing, films, and polymer modifications.

Another type of polybutylene known in the art is elastomeric polybutylene. Elastomeric polybutylene, like conventional polybutylene, is highly stereoregular. However, unlike conventional polybutylene, it has a lesser degree of crystallinity, and exhibits physical properties which more closely parallel those of thermoplastic elastomers such as commercial block copolymers based on styrene and diolefins or complex blends of polypropylene with elastomeric copolymers of ethylene and propylene.

A prominent feature of elastomeric polybutylene is its substantially suppressed level of crystallinity compared to conventional polybutylenes. A companion feature of the elastomeric polybutylene, one which makes it unique among the large number of polyolefins produced with stereoselective catalyst, is the fact that this suppression of crystallinity is achieved without a corresponding large increase in amount of easily extractable polymer (soluble in refluxing diethyl ether). This unusually low ether solubles content makes possible film use for medical and food packages that cannot tolerate substantial leaching of the plastic into the solutions or food.

Another distinguishing feature of the novel elastomeric polybutylene is its 13 C NMR spectrum. The 13 C NMR method provides detailed information about the configuration and conformation of short sections of polymer chains. A comparison of the 13 C NMR spectra of conventional polybutylene with that of the novel elastomeric polybutylene indicates a significant difference between the polymers, even though they both have a very high degree of steric order. The difference shows up in the elastomeric polybutylene as a higher proportion of polymer which comprises of short sequences of frequent tactic inversion alternating with longer isotactic sequences. This indicates a molecular structure of relatively short average isotactic sequences, which contrasts strikingly with the structure of long average isotactic sequences of conventional polybutylene. The elastomeric polybutylene consists mainly of isotactic blocks, interrupted by inversions of only one or a few monomer units largely in alternating (syndiotactic) stereochemical configurations.

Elastomeric polybutylene having a wide range of molecular weights may be produced. Number average molecular weights (Mn) may be from 20,000 to 300,000 and weight average molecular weights (Mw) from 150,000 to 2,200,000. A characteristic of the novel elastomeric polybutylene of this invention is a narrow molecular weight distribution, as indicated by the ratio of Mw/Mn (Q-value) which is typically in the order of 70 to 75% wt or less than the Q-value of conventional polybutylene.

Both conventional and elastomeric isotactic polybutylene are unique compared to other commercial polyolefins in that they are capable of existing in several crystalline modifications which can be isolated in almost pure form. Conventional isotactic polybutylene typically first solidifies from the melt in the crystal form known as Type II. Type II is unstable with respect to Type I and converts to Type I at a rate depending on a variety of factors, such as molecular weight, tacticity, temperature, pressure, and mechanical shock. Properties of the several crystal forms of conventional isotactic polybutylene are well known. The transformation of Type II to Type I has a marked effect on the physical properties. For example, density, rigidity and strength are increased.

Unlike conventional polybutylenes, our unique elastomeric polybutylene crystallizes from melt in the form of crystal Type II, which is not distinctly transformed to crystal Type I over a period of hours or days. The physical properties of this type of elastomeric polybutylene (ELPB) made with SHAC™ 201 catalyst is significantly different from the polymer made from the conventional isotactic polybutylene (I-PB) with titanium trichloride (TICl 3 ) as catalyst and the short stereoblock polybutylene (SSPB) made with a SHAC™ 103 catalyst.

The novel elastomeric polybutylene can also be made with the catalyst system disclosed in U.S. Pat. No. 4,971,936. The catalyst comprises the reaction of a magnesium alkoxide and a tetravalent titanium halide wherein the reaction takes place in the presence of an electron donor which is selected from the group consisting of 3-methyl-veratrole, 3-methoxy-veratrole, 4-nitro-veratrole and 4-methoxy-veratrole.

Table 1 lists the general physical properties of the elastomeric polybutylene (ELPB) of this invention. Also shown in Table 1, for comparison, are corresponding properties of a butene-1 homopolymer (I-PB) produced on a commercial scale in a solution process with TIC13 as catalyst and those of butene-1 homopolymer (SSPB) with a SHAC™ 103 catalyst.

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Catalyst SHAC 201 SHAC 103 TiCl.sub.3

% Isotacticity

<70 71-80 >80

Liso <20 <25 >85

% Syndiotacticity**

>10 5-10 <5

Melting Point, °C.

1st Heat <105 100-118 >120

2nd Heat <101 98-110 >110

% Crystallinity

<25 25-40 >40

Tensile Strength

<3,000 3,000-4,500

>4,500

@ Break psi

Elongation at

>500 300-600 <400

Break, %

Yield Strength, psi

No Yield 400-1,700

>1,700

Point

Tensile Set, %

<170 150-200 >200

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*Data mostly from the U.S. Statutory Invention Registration No. H179.

As shown in Table, 1, the elastomeric polybutylene is very distinctly different from the other type polybutylenes in basic molecular configuration in such properties as tacticity, and isotactic block length (Liso). They are also different in physical properties such as melting points, percent (%) crystallinity, tensile break strength, elongation, tensile yield strength and percent (%) tensile set. The no tensile yield point and low tensile set of the elastomeric polybutylene is particularly suitable in applications pertaining to the replacement of PVC film as film wrap and in the manufacture of fibers where high resiliency is required.

The invention is further described by the following non-limiting examples and data tables.

Butene polymerizations were conducted in a one gallon stainless steel autoclave utilizing 1.7 liters of butene-1 monomer. The magnesium alkoxide compound of the formula:

Mg.sub.4 (OCH.sub.3).sub.6 (CH.sub.3 OH).sub.10 (1,3-0,OH-C.sub.6 H.sub.4).sub.2, M

(wherein (1,3-O,OH-C 6 H 4 ) 2 , M is a resorcinate) was used to prepare the procatalyst. The magnesium alkoxide compound was prepared by the dropwise addition of tetraethoxysilane stabilized 12% magnesium methoxide solution to a solution of resorcinol in methanol. Partial azeotropic desolvation was carried out by slurrying 40 grams of M in 300 grams of cyclohexane containing 120 grams of tetraethoxysilane and boiling the mixture until a decrease of 20 to 30% in solvent volume had occurred.

The procatalyst was prepared by stirring 7.8 grams of dissolved M with 12 mmoles of 4-methoxyveratrole in 200 ml of a 50-50 titanium tetrachloride-chlorobenzene solution for one hour at 115° C. followed by two washes at 115° C. with fresh 200 ml portions of that solvent mixture, then a quick rinse (less than 10 minutes) with 100 ml of fresh titanium tetrachloridechlorobenzene solvent mixture. Excess titanium was removed by thorough isopentane rinsing and the catalyst was dried under moving nitrogen at 40° C. Ti content was 3.55%. A portion of the dry procatalyst powder was then made into a 5% slurry in mineral oil.

In the following polymerizations, triethyl aluminum was used as a 0.28 molar in isooctane. Tiisobutyl aluminum was used as a 0.87 molar solution in heptane. Diethylaluminum chloride was used as a 1.5 molar solution in heptane.

The polymerization was carried out by mixing 0.015 to 0.003 mmol of procatalyst, aluminum alkyl, and selectivity control agent (SCA) then, after 20 minutes, injecting the mixture into 1.8 liters of liquid butene-1 in the one gallon stainless autoclave. At the end of 90 minutes the reactions were terminated by injecting 600 ml of isopropyl alcohol to the cooled reactor prior to venting the unreacted monomer. Additional details regarding the catalysts utilized is summarized in Tables IIA and IIB.

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Catalysts With Substituted Veratrole

As Electron Donors Internal (SCA)

Catalyst Electron Donor Mg Ti

# Name Mmol % Wt % Wt

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1 Vera 8.6 20.2 3.01

2 30 MV 10 17.9 5.78

3 40 MV 12 18.8 3.55

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Note:

Vera = Veratrole

30 MV = 3 Methoxyveratrole

40 MV = 4 Methoxyveratrole

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Autoclave Runs to Produce ELPB With Veratrole-Based

Catalysts (1.8 liters butene-1, 0.01-0.02 mol Ti, 60° C., 90

min.)

SCA/Ti TEA/Ti Yield

Run # Cat. # SCA mol/mol

mol/mol Kg/g cat.

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1 1 CYANCL 4 105 8.0

2 2 DIBDMS 5 107 4.2

3 3 None -- 70 7.0

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CYANCL = Cyanuric Chloride

DIBDMS = Diisobutyl dimethoxysilane

TEA = Titanium

SCA = Selectivity Control Agent

The tensile data and NMR results are shown in Tables IIC and IID, respectively.

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Tensile Data of the ELPB Produced

Run Tbreak Tset Tyield

Elong.

# psi % psi %

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1 2751 162 No 485

2 1932 166 Yield 346

3A 1609 110 Point 557

3B 100 600

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NMR Result of the ELPB Produced

Run # ISO % Liso Units

Syn %

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1 68 17 13

2 64 16 14

3 60 10 16

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The low tensile set values and no yield point of the novel elastomeric polybutylene makes it suitable in film applications which requires good recovery upon stretch and in fiber applications which requires good recovery upon compression.

The ELPB product from run #3 in Example 1 was further characterized based on its physical properties. These properties are summarized in Table IIIA.

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Physical Properties of ELPB Product from

Run #3, Example 1

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% Isotacticity 60

Liso, Units 10

% Syndiotacticity 16

Melting Point, °C.

1st Heat 101.5

2nd Heat 100.3

% Crystallinity 20

Tensile Strength at Break, psi

1609

Elongation at Break, %

557

660

Yield Strength No Yield Point

Tensile Set, % 110

120

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The ELPB because of its low tensile set and no tensile yield point is very suitable for the manufacture of wrapping films for fresh meat and produce and in fibers for carpets.

While this invention has been described in detail for the purpose of illustration, it is not to be construed as limited thereby but is intended to cover all changes and modifications within the spirit and scope thereof.