DE4329292A1 - Propylene polymers containing nucleating agents - Google Patents

Abstract

Propylene polymers containing a) a propylene copolymer comprising from 85 to 99% by weight of a propylene polymer containing from 0 to 2% by weight of further copolymerised C2-C10-alk-1-enes, and from 1 to 15% by weight of a propylene-ethylene copolymer having an ethylene content of from 40 to 80% by weight, and b) a nucleating agent, where from 0.01 to 2 parts by weight of the nucleating agent b) are employed per 100 parts by weight of the propylene copolymer a). The propylene polymers according to the invention are particularly distinguished by significantly improved impact strength and high rigidity.

Description

The present invention relates to propylene polymers, including tend

• a) a propylene copolymer
  85 to 99 wt .-% of a propylene polymer with 0 to 2 wt .-% further, copolymerized C₂-C₁₀-alk-1-ene and
  1 to 5 wt .-% of a propylene-ethylene copolymer with an ethylene content of 40 to 80 wt .-%, and
• b) a nucleating agent,
  wherein 0.01 to 2 parts by weight of the nucleating agent b) are used per 100 parts by weight of the propylene copolymer a).

The present invention also relates to a method for Production of these propylene polymers, and films and mold bodies made from these propylene polymers.

Available by polymerization on Ziegler-Natta catalysts Propylene polymers are already in a number of patents writings have been described. From US-A 4 260 710 it is known Homo- and copolymers of α-olefins by polymerization with With the help of Ziegler-Natta catalysts in a stirred tank put. The catalyst components used contain u. a. Compounds of polyvalent titanium, aluminum halides and / or alkyls, and electron donor compounds, wherein mostly silanes, esters, ethers, ketones or lactones are used den (EP-B 14 523, EP-B 45 977, EP-B 86 473, EP-A 171 200, US-A 4,857,613).

Furthermore, there are a number of methods for representing Propylene-ethylene copolymers using a Ziegler-Natta kata lysator systems known (US-A 4 454 299, US-A 4 455 405, ZA-B 0084/3561, ZA-B 0084/3563, ZA-B 0084/5261, GB-B 1 032 945, EP-A 355 603), in which one first gaseous propylene in polymerized in a first reaction stage and obtained therefrom Liche homopolymer then in a second reaction stage brings where a mixture of ethylene and propylene add is merized. The procedure is usually carried out at elevated pressure  and in the presence of hydrogen as a molecular weight regulator leads. By polymerizing a mixture of propylene and ethylene to the propylene homopolymer become its property ten changed significantly because copolymers and homopoly partially merisate in terms of strength and durability make a significant difference. The polymer mixtures available here usually have good impact strength, but also one significantly reduced stiffness compared to pure polypropylene on. For some areas of application, however, are predominant Copolymers needed, which in addition to one for practical purposes sufficiently good impact strength also high rigidity point. In addition, the copolyumisates often still contain Catalyst residues, especially titanium and chlorine, what their application availability and a. restricted in the food and hygiene area.

Another way to ge the properties of polyolefins to be able to change is to add them offset. In particular, light stabilizers are found as additives sensors, lubricants, viscosity improvers, UV absorbers, Radical scavengers and nucleating agents use, taking under the latter substances are to be understood which contribute to the nucleation accelerate the crystallization from the melt, causing can improve the crystallinity of the polyolefins (K. Stoeckhert "Plastic Lexicon", 7th edition, Carl Hanser Verlag, Munich Vienna, 1981). From the U.S. 4,016,118 is in this context known, polyolefins with 0.1 to 0.7 wt .-% dibenzylidene sorbitol to offset in this way the optical properties of the Polyolefins, especially to improve their transparency. Out however, this patent does not show how polyolefins with improved impact strength at a consistently high level Stiffness can be produced.

From DE-A 41 19 282 it is known by adding nucleic acid agents for certain propylene polymers places that u. a. through improved impact resistance the highest possible rigidity. So nucleated Propylene polymers are particularly suitable as materials for Foils and moldings. For certain areas of application it is however required, starting from the be in DE-A 41 19 282 wrote nucleated propylene polymer products which, with sufficient stiffness, is distinguish better impact strength.

The present invention was therefore based on the object of this To remedy disadvantages and propylene polymers with ver as possible improved impact strength with consistently high rigidity develop. It was with regard to that in the  DE-A 41 19 282 products described unexpectedly that propylene polymers with a very specific ethylene content sometimes have improved impact strength.

The propylene polymers according to the invention contain a Propylene copolymer a), which from 85 to 99 wt .-% of a Propylene polymer with 0 to 2 wt .-% further, einpolymeri Siert C₂-C₁₀-alk-1-ene and 1 to 15 wt .-% of a propylene-ethyl len copolymer with an ethylene content of 40 to 80 wt .-% consists. Such a propylene copoly is preferred merisat a) used, which consists of 88 to 97 wt .-% of a Propylene polymer with 0 to 1 wt .-% further, einpolymeri Siert C₂-C₁₀-alk-1-ene and 3 to 12 wt .-% of a propylene-ethyl len copolymer with an ethylene content of 40 to 75 wt .-%, in particular from 42 to 70% by weight. Particularly preferred Propylene polymers contain a propylene-ethylene copolymer with an ethylene content of 42 to 60 wt .-%. Under a polymer based C₂-C₁₀-alk-1-enes are understood to mean especially ethylene, But-1-ene, pent-1-ene and hex-1-ene, preferably ethylene and But-1-en can be used. For the propylene according to the invention Such propylene is also particularly suitable for polymers copolymer a) in which the propylene polymer contains no further contains polymerized C₂-C₁₀-alk-1-ene, so that this as Propylene homopolymer can be called.

The production of these in the propylene poly according to the invention Propylene copolymers a) containing merisates can in the ex Lichen reactors used for the polymerization of propylene either carried out batchwise or preferably continuously become. Suitable reactors include a. continuously operated Stirred kettle, whereby one usually ge a series of one after the other switched stirred kettles. The reactors contain a Fixed bed made of finely divided polymer, which is usually is kept in motion by stirring. The manufacturing process can be in solution, in a slurry or in the gas phase be carried out, the gas phase polymerization being preferred is.

Furthermore, the manufacturing process with the in the Polyme conventional Ziegler-Natta catalysts leads. These contain u. a. in addition to a titanium-containing Solid component still a cocatalyst. As a cocatalyst an aluminum connection can be used. Preferably in addition to this aluminum compound as a further component of the Co catalyst still used an electron donor compound.  

To produce the titanium-containing solid component as Titanium compounds in general halides or alcoholates of tri- or tetravalent titanium is used, the chlorides of Titanium, especially titanium tetrachloride, are preferred. Advantage the titanium-containing solid component contains a fine partial carrier, for which silicon and aluminum oxides, and Aluminum silicates of the gross formula SiO₂, aAl₂O₃, where a for one Value from 0.001 to 2, in particular from 0.01 to 0.5, is good have proven.

The carriers preferably used have a particle diameter from 0.1 to 1000 mm, in particular from 10 to 300 mm, a pore volume from 0.1 to 10 cm³ / g, in particular from 1.0 to 5.0 cm³ / g and a specific surface area of 10 to 1000 m² / g, in particular from 100 to 500 m² / g.

Next in the manufacture of the titanium-containing solid component u. a. Compounds of magnesium used. As a sol come especially magnesium halides, magnesium alkyls and Magnesium aryls, as well as magnesium alkoxy and magnesium aryloxy compounds into consideration, preferably magnesium dichloride, Magnesium dibromide and magnesium di (C₁-C₁₀ alkyl) compounds be used. In addition, the titanium-containing solid compo nente halogen, preferably chlorine or bromine, contain.

The titanium-containing solid component also contains Electron donor compounds, for example mono- or poly functional carboxylic acids, carboxylic anhydrides and carboxylic acid esters, also ketones, ethers, alcohols, lactones, and phosphorus and organosilicon compounds. Are preferred as Electron donor compounds within the titanium-containing solid Substance component phthalic acid derivatives of the general formula I

used, where X and Y each represent a chlorine atom or a C₁- to C₁₀ alkoxy or together represent oxygen. Especially preferred electron donor compounds are phthalic acid esters, where in the case of X and Y, a C₁-C₈ alkoxy radical, for example a methoxy, Ethoxy, propyloxy or a butyloxy radical.

More preferred electron donor compounds within the titanium-containing solid components are u. a. Diester of 3- or 4-membered, optionally substituted cyclo  alkyl-1,2-dicarboxylic acids, and monoesters of, if appropriate substituted benzophenone-2-carboxylic acids. As hydroxy connections with these esters become those with esterification cracks tion usual alcohols used, u. a. C₁ to C₁₅ alkanols, C₅- to C₇-cycloalkanols, which in turn tra C₁ to C₁₀ alkyl groups gene can, further C₆ to C₁₀ phenols.

The titanium-containing solid component can be prepared in a manner known per se Methods are made. Examples include: a. in the EP-A 45 975, EP-A 45 977, EP-A 86 473, EP-A 171 200, GB-A 2 111 066 and US-A 4 857 613.

In the production of the titanium-containing solid component preferably the following three-stage process is used:

In the first stage, you first add a finely divided tear ger, preferably silicon dioxide or SiO₂, aAl₂O₃ - where a for one Number in the range from 0.001 to 2, in particular in the range from 0.01 stands up to 0.5 - with a solution of the magnesium-containing compound in a liquid alkane, after which this mixture is 0.5 to 5 Hours was stirred at a temperature between 10 and 120 ° C. Preferably, 0.1 to 1 mol of the is used per mole of the carrier Magnesium compound. Then you add under permanent Stir a halogen or a hydrogen halide, in particular Chlorine or hydrogen chloride in at least two times, preferred in at least a five-fold molar excess, based on the magnesium-containing compound. After about 30 to 120 minutes the solid is separated from the liquid phase.

In the second stage you get what you get in this way Product in a liquid alkane and then adds a C₁ to C₈-alkanol, especially ethanol, a halide or an alcoholate of trivalent or tetravalent titanium, especially titanium tetra chloride, as well as an electron donor compound. Doing so per mole of magnesium of the solid obtained from the first stage substance 1 to 5 mol, in particular 2 to 4 mol, alkanol, 2 to 20 mol, in particular 4 to 10 mol, of the trivalent or tetravalent Titanium and 0.01 to 1 mol, in particular 0.1 to 1.0 mol, of Electron donor compound. This mixture will at least for one hour at a temperature between 10 and 150 ° C stirred, the solid substance thus obtained is then filtered off and with a liquid alkane, preferably with hexane or heptane .

In the third stage, you extract that from the second stage solid obtained for a few hours at temperatures between 100 and 150 ° C with excess titanium tetrachloride or  a solution of titanium tetrachloride in excess an inert solvent, preferably an alkylbenzene, where ent at least 5 wt .-% titanium tetrachloride holds. Then you wash the product with a liquid Alkane until the wash liquid contains titanium tetrachloride is less than 2% by weight.

The titanium-containing solid component obtainable in this way is using a cocatalyst as a Ziegler-Natta catalyst system used. Aluminum compounds come as the cocatalyst in question.

Aluminum compounds suitable as cocatalyst are, in addition to tri alkyl aluminum also those compounds in which an alkyl group by an alkoxy group or by a halogen atom, at for example by chlorine or bromine. To be favoured Trialkylaluminum compounds used, the alkyl groups each Weil have 1 to 8 carbon atoms, for example trimethyl, tri ethyl or methyl diethyl aluminum.

In addition to the aluminum compound, preference is also given to further cocatalyst electron donor compounds such as as mono- or polyfunctional carboxylic acids, carboxylic acid anhydrides and carboxylic acid esters, also ketones, ethers, alcohols, Lactones, as well as organophosphorus and organosilicon compounds. Be preferred electron donor compounds are silicon organic compounds of the general formula II

R¹ _n Si (OR²) _4-n II

wherein R¹ is the same or different and is a C₁ to C₂₀ alkyl group, a 5- to 7-membered cycloalkyl group, which in turn can carry a C₁ to C₁₀ alkyl group, or a C₆ to C₂₀ aryl or arylalkyl group, R² is the same or different is and is a C₁ to C₂₀ alkyl group and n for the Numbers 1, 2 or 3 stands. Those are particularly preferred Compounds in which R¹ is a C₁ to C₈ alkyl group or a 5- to 7-membered cycloalkyl group, and R² is a C₁ to C₄ alkyl group means and n stands for the numbers 1 or 2.

These compounds include, in particular, dimethoxydiisopropyl silane, dimethoxy-sec-butylisopropylsilane, dimethoxyisobutyliso propylsilane, dimethoxydiisobutylsilane, dimethoxydicyclopentyl highlight silane and diethoxyisobutylisopropylsilane.  

Such catalyst systems are preferably used in which the atomic ratio between aluminum from the aluminum compound and titanium from the titanium-containing solid component 10: 1 to 800: 1, in particular 20: 1 to 200: 1, and the molar ratio between the aluminum compound and the as a cocatalyst set electron donor compound 1: 1 to 100: 1, in particular 2: 1 to 80: 1. The individual catalyst components can in in any order individually or as a mixture of two components be introduced into the polymerization system.

The production of the propylene poly in the invention Propylene copolymers a) containing merisates are carried out normally usually after a two-stage process, in which he Most polymerization stage propylene, optionally in the presence further C₂-C₁₀-alk-1-ene, is polymerized and then in a second polymerization stage that from the first Polymerisa tion stage discharged polymer a mixture of propylene and Polymerized ethylene.

The polymerization of propylene is in the first polymer onsstufe at a pressure of 20 to 40 bar, a medium Ver because of the reaction mixture from 1 to 5 hours and one Temperature from 60 to 90 ° C carried out. Are preferred Pressures from 20 to 35 bar, average residence times from 1.5 to 4 Hours and temperatures from 65 to 85 ° C. In a preferred one The procedure is chosen so that in the first polymerization stage per mmol of the aluminum component 0.05 up to 2 kg, in particular 0.1 to 1.5 kg, of polypropylene become.

The monomer mixture can in addition to the propylene in a small order catch further C₂-C₁₀-alk-1-enes, especially ethylene, but-1-enes, Pent-1-ene or hex-1-ene included. In this case Relationship between the partial pressure-es propylene and that of the C₂-C₁₀-Alk-1-ens usually to 20: 1 to 500: 1, in particular set to 50: 1 to 200: 1. Preferably, however, in the first polymerization stage to include other C₂-C₁₀-alk-1-enes completely dispensed with.

The propylene polymer formed is made with the catalyst discharged in the first polymerization stage and in the second Polymerization stage transferred where this is a mixture Polymerized propylene and ethylene. The one in the second The prevailing polymerization stage pressure is 7 bar, preferred 10 bar, below that of the first polymerization stage and is 5 up to 30, preferably 10 to 25 bar. The temperature is in the second polymerization stage at 40 to 100 ° C, preferably at 50  set to 90 ° C, the mean residence times are Range of 1 to 5 hours, especially in the range of 1.5 to 4 hours.

The ratio of the partial pressures between propylene and ethylene lies in the usual in the production of such copolymers Chen ranges, preferably in the range from 4: 1 to 1: 1, in particular those in the range from 3.5: 1 to 1.2: 1. In addition to propylene and ethylene can still small amounts in the second polymerization stage of C₄-C₁₀-alk-1-enes, for example of but-1-ene, pent-1-ene or Hex-1-enpolymerized, in which case the Ratio of the partial pressures between these C₄-C₁₀-alk-1-enes and the propylene not more than 1: 100, especially not more than 0.5: 100. The weight ratio between those in the he most and the Mo converted in the second polymerization stage nomeren is usually set so that in the first Po lymerisation stage more monomer is implemented. Preferably the weight ratio between those in the first and those in the reacted monomers converted in the second polymerization stage that it is in a range from 5: 1 to 100: 1, especially in loading ranges from about 6: 1 to 50: 1.

There is also the possibility of adding to the reaction mixture the second polymerization stage a C₁ to C₈ alkanol, in particular dere a C₁-C₄ alkanol to introduce, which the activity of Ziegler-Natta catalyst influenced. Well suited for that Alkanols are u. a. Methanol, ethanol, n-propanol, n-butanol and especially isopropanol. The amount of added In this case, C₁-C in alkanols should expediently be dimensioned in this way that the molar ratio between the aluminum compound and the C₁-C₃ alkanol 0.1: 1 to 10: 1, in particular 0.2: 1 to 5: 1 is.

The molecular weight of the polymers obtainable here can be as usually by adding regulators, especially hydrogen to be controlled.

The propylene copolymers a) obtainable in this way are in the propylene polymers according to the invention together with a Nucleating agent b) used, which by definition the Accelerate nucleation during crystallization from the melt nigt. The nucleating agents are those in plastic technology usually used nucleating agents, for example mineral additives such as talc, silica or kaolin, or organic compounds such as mono- and poly  carboxylic acids and their salts, or polymers such as ethylene Acrylic ester copolymers.

Particularly preferred nucleating agents are in particular Dibenzylidene sorbitol and its C₁-C₈-alkyl-substituted derivatives, for example methyldibenzylidensorbitol, also fine talc, see above such as salts of diesters of phosphoric acid, for example the Sodium salts of the following compounds of the formulas III and IV,

wherein R³ is a branched C₃-C₈ alkyl group, especially for a tert-butyl, tert-pentyl or a tert. Hexyl group stands.

In the propylene polymers according to the invention Propylene copolymer a) and the nucleating agent b) in such Ratios used that per 100 parts by weight of Propylene copolymer a) 0.01 to 2 parts by weight, in particular 0.05 to 1.5 parts by weight of the nucleating agent b) are used become.

The production of the propylene polymers according to the invention follows by adding the nucleating agent used in each case b) to the propylene copolymers a) in the in the plastic ver work usually used to mix substances Apparatus, for example in drum mixers, in mills, in Screw or disk extruders, in rolling mills or kneaders. The propylene copolymer a) and the nucleating agent b) in the mixing apparatus usually at a temperature of 150 up to 250 ° C, in particular from 180 to 240 ° C, mixed together. The mixing process is usually carried out by pressing 1 up to 100 bar and average residence times from 0.5 to 60 minutes. The exact values for pressure and mean residence time are depending on the mixing equipment used.  

The propylene polymers according to the invention are characterized u. a. due to a very high impact strength combined with a high one Stiffness. In addition, their tendency to break white decreased. After a procedural point of view, they are not very expensive manufacturing process by simply adding a nu lubricant b) are available and are particularly suitable for Manufacture of foils and moldings.

example Examples 1 and 2 and Comparative Examples A and B A. Propylene copolymers used example 1

A propylene copolymer (1) was used which consisted of 90.2% by weight of a propylene homopolymer and 9.8% by weight of a propylene copolymer with 57% by weight of copolymerized ethylene
and a melt flow index of 14.2 g / 10 min, at 230 ° C and
2.16 kp, according to DIN 53 735.

Example 2

A propylene copolymer (2) was used, which consists of
92.7 wt .-% of a propylene homopolymer and 7.3 wt .-% of a propylene copolymer with 48 wt .-% einpoly merized ethylene
and a melt flow index of 3.5 g / 10 min, at 230 ° C and
2.16 kp, according to DIN 53 735.

Comparative Example A

A propylene copolymer (A) was used, which consists of
90.1% by weight of a propylene homopolymer and 9.9% by weight of a propylene copolymer with 28% by weight of a polymerized ethylene
and a melt flow index of 13.2 g / 10 min at 230 ° C and
2.16 kp, according to DIN 53 735.

Comparative Example B

A propylene copolymer (B) was used, which consists of
92.5% by weight of a propylene homopolymer and
7.5 wt .-% of a propylene copolymer with 84 wt .-% einpoly merized ethylene
and a melt flow index of 13.8 g / 10 min at 230 ° C and
2.16 kp, according to DIN 53 735.

B. Mixing with the nucleating agent

The propylene copolymers of Examples 1, 2 and the comparison Examples A, B were in a company twin screw extruder Werner & Pfleiderer ("ZSK 30" or "ZSK 40") at one temperature of 220 ° C, a pressure of 5 bar and an average residence time of 1.5 minutes with a nucleating agent. The one there The polymers used were in the form of semolina or granules introduced the twin screw extruder. As a nucleating agent the dibenzylidene sorbitol (hereinafter referred to as "I"), fine talc ("II"), the sodium salt of the compound of formula III, (Page 9) ("III") and the sodium salt of the compound with the For mel IV (page 9) ("IV") used, with R3 in both cases Weil stands for a tert-butyl group. The in the individual ver can use the nucleating agent used with each because of the quantities given in the table below the.

The rigidity and impact resistance of this way obtained nucleated polymers are in the following Table listed.

Determination of white break

The white area was determined with the help of a DIN darting device 53 443 Part 1 determined, a dart with a mass of 250 g, a 5 mm diameter impact body and a calotte radius of 25 mm was used. The fall height was 50 cm.

An injection molded round disk with a was used as a test specimen Diameter of 60 mm and a thickness of 2 mm are used. Of the Test specimens were at a melt temperature of 250 ° C and a Injection molded tool surface temperature of 30 ° C.

The test was carried out at a temperature of 23 ° C, each Test specimen was subjected to only one impact test at a time. There at first the test specimen was placed on a support ring, without being clamped, and then the Fall bolt triggered. In each case 5 Test specimen checked.

The diameter of the visible white break marking is in mm given and was determined by this on the Side of the round disc facing away from the impact in the flow direction and sen krecht measured this and determined the mean from both values.

The table shows that the invention Propylene copolymers of Examples 1 and 2 of which the Comparative Examples A and B u. a. through an increased impact resistance excellence with similarly high rigidity. Furthermore is the case with the propylene copolymers according to the invention games 1 and 2 reduced the tendency to break white.

Claims (10)

1. Propylene polymers containing

• a) a propylene copolymer

85 to 99 wt .-% of a propylene polymer with 0 to 2 wt .-% further, copolymerized C₂-C₁₀-alk-1-ene and
1 to 15 wt .-% of a propylene-ethylene copolymer with an ethylene content of 40 to 80 wt .-%, and

• b) a nucleating agent,

wherein per 100 parts by weight of the propylene copolymer a) 0.01 to 2 parts by weight of the nucleating agent b) be set. 2. Propylene polymers according to claim 1, wherein the propylene copolymer a)
88 to 97 wt .-% of a propylene polymer with 0 to 1 wt .-% further, copolymerized C₂-C₁₀-alk-1-ene and
3 to 12 wt .-% of a propylene-ethylene copolymer with an ethylene content of 40 to 80 wt .-%. 3. Propylene polymers according to claims 1 or 2, wherein the Propylene copolymer a) a propylene homopolymer contains. 4. Propylene polymers according to claims 1 to 3, wherein the Propylene copolymer a) a propylene-ethylene copolymer contains with an ethylene content of 42 to 70 wt .-%. 5. Propylene polymers according to claims 1 to 4, wherein as Nucleating agent b) Dibenzylidensorbitol, C₁-C₈-alkyl substituted dibenzylidene sorbitol, fine talc or salts of diesters of phosphoric acid can be used.   6. Propylene polymers according to claims 1 to 5, wherein per 100 parts by weight of the propylene copolymer a) 0.05 to 1.5 parts by weight of the nucleating agent b) are used. 7. Process for the preparation of propylene polymers according to Claims 1 to 6, characterized in that one Propylene copolymer a, and the nucleating agent b) in a mixing apparatus at a temperature of 150 to 250 ° C united with each other. 8. Films and moldings from the propylene polymers according to Claims 1 to 6.