DE10017312A1 - Grafted polyolefins useful as blend components for polymer blends, prepared by mixing a polyethylene or ethylene copolymer in the solid state with a mixture containing at least one graft monomer - Google Patents

Abstract

Grafted polyolefins (I) are prepared by: (A) mixing a polyethylene or ethylene copolymer in the solid state with a mixture containing at least one graft monomer at a mixing temperature below the softening point and below the crystallite melting point of the polyolefin; and (B) at least partial polymerization of the graft monomers. An Independent claim is included for polymer blend containing the grafted polyolefin (I).

Description

The invention relates to a method for producing ge grafted polyolefins.

The invention further relates to those obtainable by the process Chen grafted polyolefins, their use as a blend nente and such blends.

A known problem with polymer blends is the incompatibility of many polymers with each other (undesired separation and bad phase connection). For example, poly olefins and styrene polymers such as polystyrene, HIPS (high impact Polystyrene, impact-resistant polystyrene), ABS (acrylonitrile butadiene Styrene) and ASA (acrylonitrile-styrene-alkyl acrylate) with no blend produce advantageous properties because polyolefins and Styrene polymers are incompatible.

To improve the tolerance, you can, for example, the Modify polyolefins chemically, for example by incorporating Sty rol side chains in the polyolefin. A known procedure for this is reactive extrusion, in which the polymer to be modified (here the polyolefin) melted in an extruder and intimately mixed with the modifying monomer (here e.g. styrene) becomes. The residence time of the polymer is ver in an extruder equally short, typically only a few minutes. To the required chemical connection (grafting) of the styrene to the To ensure polyolefin must be due to the short residence time the extruder temperature be relatively high, e.g. B. 180 to 300 ° C. This high temperature damages the polymer (thermal degradation). Another disadvantage of the short dwell time is that it is local can form higher concentrations of the polymerization initiator nen (inhomogeneous distribution). This leads to inhomogeneous products and speck formation. In addition, reactive extrusion has the aftermath partly that the styrene side chains are often very short, what the Compatibility with styrene polymers only insufficiently improved (each the shorter the styrene side chains, the worse the tolerability speed).

The task was to remedy the disadvantages described. In particular, the task was to provide a method that works at gentler temperatures. In addition, that should Process a grafted polyolefin with longer styrene sides  chains and thus better compatibility with styrene polymers deliver.

Accordingly, the process defined at the outset was found. It is characterized in that one

• 1. a polyolefin selected from polyethylene and ethylene copolymers, in the solid state at a mixture temperature T _M with a mixture M containing at least one grafting monomer, in contact and swell, the mixture temperature T _M below the softening temperature T _E and is below the crystalline melting temperature T _{K of} the polyolefin, and
• 2. then partially or completely the graft monomers polymerized.

In addition, the grafted ones obtainable by the method were used Polyolefins, their use as blend components and such Found blends.

The polyolefin is selected from polyethylene and ethylene copoly meren.

Any commercially available polyethylene is suitable as polyethylene. Polyethylene is produced in a manner known to the person skilled in the art, for example in the gas phase using the high pressure process with acid as a catalyst, in the low pressure process with Ziegler or Phillips catalysts, or in the liquid phase in the suspension proceed in the presence of gasoline or other hydrocarbons fen or in a similar solution.

Polyethylene, which is in a gas phase vortex, is particularly suitable bed process using (usually supported) Catalysts is made, e.g. B. Lupolen® (Elenac).

Polyethylene is particularly preferred, which using Metallocene catalysts is produced. Such polyethylene is z. B. commercially available as Luflexen® (Elenac). The metal Oxene catalyst system is described in more detail below.

The following compounds of the general formula I are suitable as metallocene complexes:

in which the substituents have the following meaning:
M titanium, zirconium, hafnium, vanadium, niobium or tantalum,
X fluorine, chlorine, bromine, iodine, hydrogen or C ₁ - to C ₁₀ -alkyl,
R ⁸ to R ^{12 are} hydrogen, C ₁ to C ₁₀ alkyl, 5- to 7-membered cycloalkyl, which in turn can carry a C ₁ to C ₁₀ alkyl as a substituent, C ₆ to C ₁₅ aryl or aryl alkyl, where optionally two adjacent radicals may together represent cyclic groups having 4 to 15 carbon atoms or Si (R ¹³ ) ₃ with
R ^{13 is} C ₁ to C ₁₀ alkyl, C ₃ to C ₁₀ cycloalkyl or C ₆ to C ₁₅ aryl,
Z for x or

stands,
being the leftovers
R ¹⁴ to R ^{18 are} hydrogen, C ₁ to C ₁₀ alkyl, 5- to 7-membered cycloalkyl, which in turn can carry a C ₁ to C ₁₀ alkyl as a substituent, C ₆ to C ₁₅ aryl or arylal mean kyl and, where appropriate, two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms, or Si (R ¹⁹ ) ₃ with
R ^{19 is} C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl or C ₃ to C ₁₀ cycloalkyl,
or wherein the radicals R ¹¹ and Z together form a group -R ²⁰ -A- in which
R ²⁰

= BR ²² , = AlR ²² , -Ge-, -Sn-, -O-, -S-, = SO, = SO ₂ , = NR ²² , = CO, = PR ²² or = P (O) R ²² ,
wherein R ²¹ , R ²² and R ^{23 are the} same or different and are a hydrogen atom, a halogen atom, a C ₁ -C ₁₀ alkyl group, a C ₁ -C ₁₀ fluoroalkyl group, a C ₆ -C ₁₀ fluoroaryl group, a C ₆ -C ₁₀ aryl group, a C ₁ -C ₁₀ alkoxy group, a C ₂ -C ₁₀ alkenyl group, a C ₇ -C ₄₀ arylalkyl group, a C ₈ -C ₄₀ arylalkenyl group or a C ₇ -C ₄₀ alkylaryl mean group or where two adjacent radicals each form a ring with the atoms connecting them, and
M ^{3 is} silicon, germanium or tin,
A -O-, -S-, NR ²⁴ or PR ²⁴ mean with
R ²⁴ C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl, C ₃ to C ₁₀ cycloalkyl, alkylaryl or Si (R ²⁵ ) ₃ ,
R ^{25 is} hydrogen, C ₁ to C ₁₀ alkyl, C ₆ to C ₁₅ aryl, which in turn can be substituted by C ₁ to C ₄ alkyl groups or C ₃ to C ₁₀ cycloalkyl
or wherein the radicals R ¹¹ and R ¹⁷ together form a group -R ²⁰ - bil.

Particularly suitable metallocene complexes are, for example DE-A 198 06 435, page 3, line 68 to page 5, line 67 described. It is expressly referred to the text passage referred.

The synthesis of such complex compounds can in itself known methods take place, the implementation of the corresponding substituted, cyclic hydrocarbon anions with halogeni that of titanium, zirconium, hafnium, vanadium, niobium or tantalum, is preferred.

Examples of corresponding manufacturing processes include. a. in the Journal of Organometallic Chemistry, 369 (1989), 359-370 described.

Mixtures of different metallocene complexes can also be used be set.

As a rule, the metallocene complexes are activated by an activator connection activated. Suitable activators are in particular Compounds that form metallocenium ions.

Suitable metallocenium ion-forming compounds are in particular their complex compounds, selected from the group of strong, neutral Lewis acids, the ionic compounds with Lewis acids Cations and the ionic compounds with Bronsted acids as Cation.

Compounds of the general formula IV are strong, neutral Lewis acids

M ⁴ X ¹ X ² X ³ IV

preferred in the
M ^{4 is} an element of III. Main group of the periodic table means, in particular B, Al or Ga,
X ¹ , X ² and X ^{3 represent} hydrogen, C ₁ - to C ₁₀ -alkyl, C ₆ - to C ₁₅ -aryl, alkyl aryl, arylalkyl, haloalkyl or haloaryl, each with 1 to 10 C atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical or fluorine, chlorine, bromine or iodine are, in particular for haloaryls, preferably for pentafluorophenyl.

As ionic compounds with Lewis acid cations are compounds of the general formula V

[(Y ^{a +} ) Q ₁ Q ₂ . , , Q _z ] ^{d +} V

suitable in which
Y is an element of I. to VI. Main group or the I. to VIII. Subgroup of the periodic table means
Q ₁ to Q _z for single negatively charged radicals such as C ₁ to C ₂₈ alkyl, C ₆ to C ₁₅ aryl, alkylaryl, arylalkyl, haloalkyl, haloaryl each having 6 to 20 C atoms in the aryl and 1 to 28 C atoms in the alkyl radical, C ₁ - to C ₁₀ -cycloalkyl, which can optionally be substituted by C ₁ - to C ₁₀ -alkyl groups, halogen, C ₁ - to C ₂₈ -alkoxy, C ₆ - to C ₁₅ -aryloxy , Silyl or mercaptyl groups
a stands for integers from 1 to 6
z for integers from 0 to 5
d corresponds to the difference az, but d is greater than or equal to 1.

Carbonium cations, oxonium cations and Sulfonium cations and cationic transition metal complexes. Ins special are the triphenylmethyl cation, the silver cation and to name the 1,1'-dimethylferrocenyl cation. Prefer to own they do not coordinate counterions, especially boron compounds gene, as they are also mentioned in WO-A 91/09882, preferred Tetrakis (pentafluorophenyl) borate.

Ionic compounds with Bronsted acids as cations and before counterions, which are likewise not coordinating, are in the WO-A 91/09882 called, preferred cation is the N, N-dimethyl anilinium.

All commercially available ethylene copoly are ethylene copolymers suitable, for example Luflexen® types (Elenac), Nordel® and Engage® (Dow, DuPont). All α-olefins are included as comonomers 3 to 10 carbon atoms suitable, in particular propylene, but-1-ene, Hex-1-ene and oct-1-ene, as well as alkyl acrylates and methacrylates with 1 to 20 carbon atoms in the alkyl radical, especially butyl acrylate. Other suitable comonomers are dienes such as. B. Butadiene, Iso pren and octadiene and dicyclopentadiene.  

They are usually statistical copolymers or Block or impact copolymers.

Block or impact copolymers of ethylene and comonomers are Polymers in which a homopolymer of Comonomers or a random copolymer of the comonomer with up to 15 wt .-%, preferably up to 6 wt .-% ethylene and then in the second stage with a comonomer-ethylene copolymer Polymerized ethylene contents of 15 to 80 wt .-%. In the As a rule, as much of the comonomer-ethylene copolymer is added siert that the copolymer produced in the second stage in the end pro has a share of 3 to 60% by weight.

The polymerization to produce the ethylene comonomer copoly mere can be done using a Ziegler-Natta catalyst system Such catalyst systems are used in particular used in addition to a titanium-containing solid component Cocatalysts in the form of organic aluminum compounds and Have electron donor compounds.

But catalyst systems based on metal can also be used ocenverbindungen or on the basis of polymerization active Metal complexes are used.

According to the process found, the polyolefin is brought into contact with a mixture M in the solid state at a mixture temperature T _M and allowed to swell. The mixing temperature T _M is below the softening temperature T _E and below the crystallite melting temperature T _{K of} the polyolefin (depending on whether the polyolefin is amorphous or (partially) crystalline). T _M min is preferably at least 10 ° C. below the lower of the two temperatures T _E and T _K. T _M is particularly preferably 20 to 160 ° C., in particular 60 to 120 ° C.

Contacting the polyolefin with the mixture M ge usually happens by combining the mixture M with the Polyolefin in a suitable container. It is preferred to use the solid polyolefin in granular form. Granular form is also understood to mean granular polymer become. Liquid mixtures M are also preferred wise, the mixture of polyolefin and mixture M after Just stand together or mix through slow Stir, swirl, shake or rotate.

According to the invention, the polyolefin is brought into contact with the mixture M. This causes the polyolefin to swell (allowing the polyolefin to swell). The subsequent polymerization of the graft monomers (step 2)) can already be started when only a small part (≧ 5% by weight of M) of the mixture M has been taken up by the polyolefin. However, the polymerization is preferably only started when at least 50, preferably 95 and particularly preferably 98% by weight of the mixture M has been taken up by the polyolefin. The duration of the contact depends, inter alia, on the amount of polyolefin, the amount of the mixture M, the mixture temperature T _M and the mixing. It is usually 0.2 to 5, preferably 0.2 to 2 hours.

The mixture M can also be added in portions or as a feed add it to the polyolefin.

Mixture M contains at least one graft monomer. The mixture preferably contains M, based on M,

• a) 90 to 99.99, preferably 98 to 99.9 and particularly preferred 98.5 to 99.8% by weight of graft monomers, and
• b) 0.01 to 10, preferably 0.1 to 2 and particularly preferably 0.2 up to 1.5% by weight of at least one polymerization initiator.

The graft monomers a) are preferably selected from styrene, Acrylonitrile and maleic anhydride. Particularly preferred graft monomers a) are styrene alone and styrene / acrylonitrile mixture The latter preferably have an acrylonitrile content of 1 to 50, in particular 10 to 40 wt .-%.

As polymerization initiators b) all initiators come from Peroxide type and / or of the azo type into consideration as well as initiators with an unstable C-C bond. T-Butylperoxypiva are preferred lat, dilauryl peroxide, 2,2'-azobis (isobutyronitrile), dibenzoyl peroxide, dicumyl peroxide and t-amyl peroxy-2-ethyl hexanoate.

Initiators b) with a decomposition temperature T _Z which is below the softening temperature T _E and below the crystallite melting temperature T _{K of} the polyolefin are particularly preferred. Such initiators are especially t-butyl peroxypiva lat, dilauryl peroxide and 2,2'-azo-bis (isobutyronitrile).

The first process step accordingly provides a solid poly olefin which contains a mixture containing graft monomers and optionally Polymerization initiator, has absorbed in whole or in part.

In the second process step (grafting reaction), the graft monomers are polymerized partially (preferably up to a conversion of ≧ 50, particularly preferably ≧ 80%) or completely. For this purpose, the temperature is preferably raised starting from the mixing temperature T _M (step 1) to a temperature greater than or equal to the decay temperature T _Z. At the temperature T _Z , the initiator b) decomposes thermally and in this way initiates a grafting reaction of the grafting monomers onto the polyolefin.

The temperature in this second process step can also be above the decomposition temperature T _Z. However, it is preferably below the softening temperature T _E and below the crystallite melting temperature T _{K of} the polyolefin, which ensures that the polyolefin remains in the solid state.

The temperature during the grafting reaction is particularly preferably equal to the decomposition temperature T _Z.

Further polymerization initiator can be used during step 2) be added. It can be the same or different from the initiator in Step 1). The feed can e.g. B. continuously or postage done on an occasional basis.

In a preferred embodiment, the polyolefin is held granules during step 1) or 2) or both steps 1) and 2) in motion. This can e.g. B. by stirring or others mechanical mixing devices or by moving the container or by blowing inert gases after the fluidized bed Principle. By moving the granules, that the grafted polyolefin is also in granular form and not "polymerized" into lumps.

The grafted obtained by the process according to the invention Polyolefin contains less annoying, due to thermal degradation stood as grafted polyolefins by reactive extrusion. It also stands out a longer chain length of the grafted on side chains.

The grafted polyolefins according to the invention are suitable as Polymer material, and especially excellent for use as a blend component in polymer blends. In particular, the grafted polyolefins can be used in polymer blends Styrene homopolymers or styrene copolymers or mixtures thereof contain. Such styrene polymers are in particular polystyrene, HIPS, ABS, ASA and AES (acrylonitrile (ethylene propylene chew Tschuk) styrene). Other suitable blend components are poly carbonates, polyamides, polyesters (e.g. polybutylene terephthalate and Polyethylene terephthalate) and polymethyl methacrylate.  

Such polymer blends preferably contain

• A) 3 to 99, preferably 5 to 95 and particularly preferably 30 to 90% by weight of at least one styrene homopolymer or styrene co polymers or their mixtures, and
• B) 1 to 97, preferably 5 to 95 and particularly preferably 10 to 70% by weight of the grafted polyolefins.

Examples

In a 2 liter round bottom flask, which had 4 notches from neck to bottom to mix the contents of the flask (prevents the polymer grits from sticking together), 150 g ground Lufle xen® 0322 H (an ethylene-but-1-ene copolymer from Elenac), 75 g styrene, 25 g acrylonitrile and 0.3 g dilauryl peroxide. The round bottom flask was mounted on a rotary evaporator (without vacuum) and rotated to move the contents of the flask. When turning, was flushed with N ₂ gas. After the Luflexen polymer had swollen in the monomer / initiator mixture for 30 minutes at 20 ° C., the polymerization was started by heating to 75 ° C. Another 6 hours later, 0.3 g of dilauryl peroxide was added again. After a further 2 hours, 0.3 g of 2,2'-azo-bis (isobutyronitrile) and after a further 2 hours again 0.3 g of 2,2'-azo bis (isobutyronitrile) were added. The resulting grafted polyolefin was then stored at 80 ° C. in vacuo until the residual monomers were removed.

Example 2

The procedure was as in Example 1 with other initiator additions ben and temperatures: 0.4 g of dilauryl peroxide was used once submitted. After 30 minutes of swelling as described, the mixture was increased the temperature first to 75 ° C and after 75 min to 80 ° C. Further 80 minutes later, 0.3 g of 2,2'azobis (isobutyronitrile) was added and polymerized for a further 80 min.

Production and testing of blends

There was a styrene-acrylonitrile copolymer made of 75 wt .-% styrene and 25 wt .-% acrylonitrile, and a viscosity number VZ (determined according to DIN 53726 as a 0.5% by weight solution in dimethylformamide at 25 ° C) of 81 ml / g.

The grafted polymer from Examples 1 and 2 was with the Sty rol-acrylonitrile (SAN) copolymer on a laboratory extruder (Fa. Haake) at 240 ° C (dosage) to 260 ° C (outlet). Out  the granules obtained were melted by injection molding at 240 ° C temperature and 60 ° C mold temperature.

The notched impact strength a _K at 23 ° C according to DIN 53753-K (edition 5/75) and the perforated notched impact strength a _KL at 23 ° C according to DIN 5 3753-L-3.0 (edition 4 / 81) measured, see table below.

table

The mechanical properties of the blends according to the invention are considerably better than that of pure SAN copolymer.

Claims (10)

1. A process for the preparation of grafted polyolefins, characterized in that

• 1. a polyolefin selected from polyethylene and ethylene copolymers, in the solid state at a mixture temperature T _M with a mixture M containing at least one graft monomer, is brought into contact and swells, the mixture temperature T _M below the softening temperature T _E and is below the crystalline melting temperature T _{K of} the polyolefin, and
• 2. then partially or completely polymerized the graft monomers.

2. The method according to claim 1, characterized in that in step 1) the mixture contains M, based on M,

• a) 90 to 99.99% by weight of graft monomers, and
• b) 0.01 to 10% by weight of at least one polymerization initiator,

and that in step 2) the graft monomers are polymerized at a temperature which is greater than or equal to the decomposition temperature T _{Z of} the polymerization initiator. 3. The method according to claims 1 and 2, characterized net that the graft monomers are selected from styrene, Acrylonitrile and maleic anhydride. 4. The method according to claims 1 to 3, characterized in net that as a polymerization initiator one of the peroxide Type or one of the azo type or mixtures thereof. 5. Process according to claims 1 to 4, characterized in that such initiators are used as the polymerization initiator, the decomposition temperature T _{Z of which is} below the softening temperature T _E and below the crystallite temperature T _{K of} the polyolefin. 6. The method according to claims 1 and 5, characterized in net that the solid polyolefin in Granulate form is present and that during steps 1) or 2) or 1) and 2) the polyolefin granules in motion holds. 7. Grafted polyolefins, obtainable by the process according to claims 1 to 6. 8. Use of the grafted polyolefins as a blend component in Polymer blends. 9. polymer blends containing grafted polyolefins according to Claim 7. 10. Polymer blends according to claim 9, containing styrene homo- or copolymers or mixtures thereof.