KR20060039980A - Composition of high melt strength polypropylene for thermoforming - Google Patents

Abstract

The present invention relates to a high-elastic polypropylene resin composition excellent in vacuum formability, and more particularly, to a long-composition using a prepolymerization catalyst prepared by adding and polymerizing an olefin monomer and a diene compound to a solid complex titanium catalyst for olefin polymerization. The present invention relates to a highly elastic polypropylene resin composition having excellent vacuum forming property by polymerizing a polyolefin into which is introduced and blending a propylene homopolymer resin.

High elastic polypropylene, prepolymerization, vacuum forming, melt strength

Description

    High elastic polypropylene resin composition excellent in vacuum forming property TECHNICAL FIELD

The present invention is a vacuum forming process by blending a polyolefin polymer and a propylene homopolymer having a long branched polymerized by using a prepolymerization catalyst in which a macromonomer is encapsulated around an alpha olefin polymerization catalyst. It is related with this excellent high elastic polypropylene resin composition.

In general, polypropylene is a general-purpose plastic having a relatively high strength and excellent mechanical properties compared to other resins, due to the crystal structure and the molecular structure of the polymer chain. Furthermore, the propylene homopolymer has excellent resistance to deformation at high temperatures, has high tensile strength and surface stiffness, and copolypropylene with irregular or block copolymerization of ethylene or butylene increases in impact strength, depending on the application.

On the other hand, polypropylene does not have satisfactory formability due to the sagging during heating of sheets or preforms compared to other plastic materials due to the weak melt tension due to the linear chain structure. I couldn't.

Therefore, in order to overcome this, various methods for increasing the melt tension of polyolefins such as polypropylene have been proposed. First, the introduction of long chain branches into polyolefins reduces the attraction between polymer chains in the processing process. It is a method of providing easy flow characteristics, and in forming processes (particularly, applications requiring dimensional stability such as large blows, etc.), long branches have high elasticity through physical crosslinking with adjacent chains. As a method of preparing a high elastic polyolefin by introducing such long branches, radicals are mainly formed on the polyolefins that have passed through a polymerization reactor through electron beam or reaction extrusion, and then reacted again to form long branches in the chain polyolefin. Was used. The second is to physically blend polyethylene into polypropylene with a very low melt index. The second method has a problem that the workability is lowered because the melt index.

Therefore, if a polymerization method and a blending method are developed in which a high elasticity polyolefin having a high elasticity useful as a molding material is directly polymerized in the polymerization step, a high elasticity can be further improved, the use of the polyolefin as a molding material can be expected to be expanded.

The present invention is to solve the problems as described above, an object of the present invention is to provide a polypropylene resin composition applicable to processes such as vacuum molding, blow molding, thermoforming by increasing the melt tension.

The polypropylene resin composition of the present invention is a macromolecular monomer capable of forming a branch in an olefin polymer prepared by prepolymerization of a solid complex titanium catalyst for olefin polymerization and an olefin / multifunctional compound. It is characterized in that it is made by blending a high elastic polyolefin polymer and a propylene homopolymer resin in which long branches polymerized using a catalyst in a form encapsulated around the catalyst (hereinafter, referred to as 'prepolymerization catalyst').

The high-strength polyolefin polymer having a long branch introduced in the present invention is polymerized by a conventional method using a prepolymerization catalyst in a form in which a high molecular weight monomer is encapsulated around the catalyst for alpha olefin polymerization. Preferred examples of the components are described in Korean Patent Registration Nos. 10-0387734 and 10-0431637. The entire contents of these two patents are intended to be incorporated herein. In summary, the catalyst component is treated by surface treatment of a solid titanium catalyst for olefin polymerization with a silane compound having two or more vinyl groups, followed by prepolymerization of the surface treated solid titanium catalyst with an olefin monomer and a diene compound. It characterized in that it is prepared by encapsulating a high molecular weight monomer.

The high-elastic polypropylene resin composition according to the present invention is 30 to 95% by weight of a polyolefin polymer (hereinafter referred to as a polymer having a long branch) obtained by polymerizing by a conventional polymerization method using the above prepolymerization catalyst. % And 5 to 70% by weight of a propylene homopolymer, and 0.05 to 0.5 parts by weight of an antioxidant based on 100 parts by weight of the resin composition.

In the present invention, the melt index ratio (a / b) of the polymer (a) and the propylene homopolymer (b) in which the long branch is introduced is preferably 0.5 to 5.0, and most preferably 0.8 to 5.0. When the melt index ratio (a / b) in the resin composition exceeds 5.0, there is a problem in that a lot of load is applied during processing and holes are formed in the sheet when the sheet is melted and the sheet is destroyed. If the melt index is less than 0.5, there is a problem in that the melt strength and thermal deflection characteristics are lowered and the thickness uniformity of the sheet is worsened.

In addition, if the content of the propylene homopolymer blended to the long branch introduced polymer is less than 5% by weight, the processing properties are lowered, and when it exceeds 70% by weight, the melt tension is lowered.

High elasticity polypropylene resin composition excellent in vacuum formability according to the present invention, if the strain rate is more than a certain value when the stretch viscosity is measured, the extension hardening phenomenon is expressed, the stretch viscosity value is larger than the value of the linear curve It is characterized by.

It is preferable that the melt strength of the high elastic polypropylene resin composition of this invention is 100 mN or more, and elasticity is 2.0 or more.

If necessary, various additives such as heat stabilizers, nucleating agents, weather stabilizers, antistatic agents, lubricants, slip agents, flame retardants, pigments, dyes, and the like may be added to the resin composition of the present invention.

In the present invention, there is no particular limitation on the method of blending the propylene homopolymer and the polymer having the long branches introduced, and a commonly known blending method may be used. Each of the above components and other additives may be added in a required amount to knead using a kneader such as a kneader, a roll, a Bambury mixer, or a single or twin screw extruder.

Since the resin composition which concerns on this invention is excellent in vacuum forming, it is suitable for manufacture of a single sheet, a multilayer sheet, and a vacuum molded article for vacuum molding.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples.

Examples and Comparative Examples

[Production example]

Polypropylene with long branches having a melt strength of 300 mN was prepared and treated according to the following method.

Preparation of Prepolymerization Catalyst

Step 1: Preparation of Magnesium Compound Solution

A mixture of 15 g of magnesium chloride (MgCl ₂ ), 4.2 g of aluminum chloride (AlCl ₃ ), and 550 ml of toluene was added to a 1.0 liter reactor equipped with a mechanical stirrer replaced with a nitrogen atmosphere, stirred at 400 rpm, and 30 ml of tetrahydrofuran. , 28 ml of butanol, 1.4 ml of ethanol, 1.5 ml of silicon tetraethoxide, and 3.0 ml of tributylphosphate were added thereto, and the temperature was raised to 105 ° C. for 4 hours. The homogeneous solution obtained after the reaction was completed was cooled to room temperature.

Step 2: preparing a solid carrier

The magnesium solution prepared in step 1 was transferred to a 1.6 L reactor maintained at 13 ° C. After stirring was maintained at 350 rpm, 15.5 ml of titanium tetrachloride (TiCl ₄ ) was added thereto, and the temperature of the reactor was raised to 90 ° C. Solid carriers were produced during this process. The reaction was continued at 90 ° C. for 1 hour and then stirring was stopped to allow precipitation of the resulting solid support. After the precipitation was completed, the solid carrier from which the supernatant was separated was washed twice with 75 ml of toluene.

Step 3: Preparation of Solid Titanium Catalyst

100 ml of toluene and 100 ml of titanium chloride (TiCl ₄ ) were added to the solid carrier, and the temperature of the reactor was raised to 110 ° C. and heated for 1 hour. After the stirring was stopped, the solid carrier was precipitated, the supernatant was separated, 100 ml of toluene and 100 ml of TiCl ₄ were added thereto, and 2.9 ml of diisobutyl phthalate was added at 70 ° C. The temperature of the reactor was again raised to 120 ° C. and stirred for 1 hour. After the stirring was stopped, the supernatant was separated, 100 ml of toluene was injected, and the temperature of the reactor was lowered to 70 ° C. and stirred for 30 minutes. After stopping the reactor stirring and separating the supernatant, 100 ml of TiCl ₄ was injected and stirred at 70 ° C. for 30 minutes to prepare a solid titanium catalyst.

Step 4: surface treatment of solid titanium catalyst

The solid titanium catalyst prepared above was washed five times with 75 ml of purified hexane, and 500 ml of hexane and 50 ml of divinyldimethyl silane were added and reacted at room temperature for 1 hour. The prepared catalyst was stored after drying in a nitrogen atmosphere. The surface treated solid titanium catalyst contained 2.5% by weight of titanium atoms.

Step 5: prepolymerization

After washing the high-pressure reactor with a capacity of 0.5 L with propylene, 2 g of the catalyst obtained in step 4, 300 ml of hexane, 6 mmol of triethylaluminum, and 20 ml of hexadiene were added, and the pressure was adjusted to 0.9 atm with ethylene, and at 20 ° C. The polymerization was carried out for 5 hours. In the prepolymerization catalyst thus obtained, the amount of the high molecular weight monomer polymerized around the catalyst was 31.0 g per 1 g of the catalyst.

polymerization

The high-pressure reactor with a capacity of 2 L was washed with propylene, and then loaded into the reactor with 20 mg of the prepolymerized catalyst prepared above in a glass bottle, and then the reactor was repeated three times in a nitrogen / vacuum state and brought to atmospheric pressure. 7 mmol of triethylaluminum, 0.5 mmol of dicyclopentyldimethoxysilane and 0.5 mmol of diisopropyldimethoxysilane were injected into the reactor. Again, 5000 Nml of hydrogen was added, and then 1,200 mL of liquid propylene was added, and then the temperature was raised to 65 DEG C while stirring the reactor, and polymerization was performed for 1 hour. After the polymerization reaction was completed, the unreacted gas was discharged, the temperature was cooled to room temperature, and the reactor was desorbed. The resulting polymer was collected separately and dried in a vacuum oven at 50 ° C. for at least 6 hours to obtain a white polymer (polymer with long branches introduced).

[Measurement of physical properties]

Measurement of physical properties of the resin composition prepared in the following Examples and Comparative Examples was performed by the following method.

Surface characteristics and thermal sagging evaluation (Heat sagging characteristics)

The resin composition in the form of pellets was molded into a sheet having a thickness of 0.5 mm using a casting apparatus in the form of a T die. The surface condition of the molded sheet was evaluated as good (○), good (◎) and poor (X). As a method for evaluating vacuum thermoforming using this sheet, the sheet was placed between two discs of 10 cm diameter, and then 200 The time when 20 mm sag in the oven of ° C was measured.

Melt strength and draw viscosity measurement

Melt strength and elongation viscosity were measured at 140 ° C. chamber temperature for strands exiting through a plate of capillary rheometer at 200 ° C. using SMER (Samsung Melt Tension Rheometer). At this time, the plate had an L / D of 16 and an acceleration ratio of 1 mm / sec.

Elastic Swell Ratio

Die Swell Ratio (hereinafter referred to as DSR) was calculated by measuring the diameter (D2) of the melt after passing through an orifice having a diameter (D1) of 2 mm in the melt index measuring device.

DSR = D2 / D1

Example 1

As identified by B-1 in Table 1, the melting index of 1.7g / 10 to 70% by weight of the polymer of the molten index 1.5g / 10min (ASTM D1238: 230 ℃, 2.16kg) in which the long branches prepared above were introduced 30 wt% of propylene homopolymer in powder (ASTM D1238: 230 ° C., 2.16 kg) was blended, 0.5 parts by weight of antioxidant was mixed with 100 parts by weight of the resin composition, and then melt mixed through a twin screw extruder to pelletize. It was. The melt index of this resin was 1.55 g / 10 min, and the properties and processing characteristics of the resin composition were evaluated by the above method.

Example 2

As identified by B-2 in Table 1, the melting index of 1.7g / 10 to 50% by weight of the polymer of 1.5g / 10min (ASTM D1238: 230 ° C, 2.16kg) in which the long branch prepared above was introduced. 50 wt% of propylene homopolymer in powder (ASTM D1238: 230 ° C., 2.16 kg) was blended, 0.5 parts by weight of antioxidant was mixed together with 100 parts by weight of this resin composition, and then melt mixed through a twin screw extruder to pelletize. . The melt index of this resin was 1.60 g / 10 min, and the properties and processing characteristics of the resin composition were evaluated by the above method.

Example 3

As identified by B-3 in Table 1, the molten index was 1.7 g / 10 to 30 wt% of the polymer having a molten index of 1.5 g / 10 min (ASTM D1238: 230 ° C., 2.16 kg) in which the long branch prepared above was introduced. 70% by weight of propylene homopolymer in powder (ASTM D1238: 230 ° C., 2.16 kg) was blended, 0.5 parts by weight of antioxidant was mixed together with 100 parts by weight of the resin composition, and then melt mixed through a twin screw extruder to pelletize. . The melt index of this resin was 1.71 g / 10 min, and the properties and processing characteristics of the resin composition were evaluated by the above method.

Comparative Example 1

As confirmed by B-4 in Table 1, the melting index of 1.7g / 10 to 10% by weight of the polymer of the molten index 1.5g / 10min (ASTM D1238: 230 ℃, 2.16kg) introduced into the long branches prepared above 90% by weight of propylene homopolymer in powder (ASTM D1238: 230 ° C., 2.16 kg) was blended, 0.5 parts by weight of antioxidant was mixed with 100 parts by weight of the resin composition, and then melt mixed through a twin screw extruder to pelletize. . The melt index of this resin was 1.73 g / 10 min, and the properties and processing characteristics of the resin composition were evaluated by the above method.

Comparative Example 2

As confirmed by B-5 in Table 1, the biaxial extruder was mixed with 0.5 parts by weight of antioxidant against 100 parts by weight of propylene homopolymer having a melt index of 1.7 g / 10 minutes (ASTM D1238: 230 ° C., 2.16 kg). Pelletized by melt mixing through. The melt index of this resin was 1.75 g / 10 min, and the properties and processing characteristics of the resin composition were evaluated by the above method.

Example 4

As identified by C-1 in Table 1, the molten index 5.0g / 10 to 70% by weight of the polymer of the molten index 1.5g / 10min (ASTM D1238: 230 ℃, 2.16kg) introduced into the long branches prepared above 30 wt% of propylene homopolymer in powder (ASTM D1238: 230 ° C., 2.16 kg) was blended, 0.5 parts by weight of antioxidant was mixed together with 100 parts by weight of the resin composition, and then melt mixed through a twin screw extruder to pelletize. . The melt index of this resin was 2.4 g / 10 min, and the properties and processing characteristics of the resin composition were evaluated by the above method.

Example 5

As confirmed by Table 2 in Table 1, the long branch prepared above was introduced into the melt index of 1.5g / 10min (ASTM D1238: 230 ℃, 2.16kg) of 50% by weight of the polymer melt index 5.0g / 10 50 wt% of propylene homopolymer in powder (ASTM D1238: 230 ° C., 2.16 kg) was blended, 0.5 parts by weight of antioxidant was mixed together with 100 parts by weight of this resin composition, and then melt mixed through a twin screw extruder to pelletize. . The melt index of this resin was 3.25 g / 10 min, and the properties and processing characteristics of the resin composition were evaluated by the above method.

Comparative Example 3

As identified by C-3 in Table 1, the melt index of the prepared long branch introduced melt index 1.5g / 10 minutes (ASTM D1238: 230 ℃, 2.16kg) 20% by weight of the polymer 5.0g / 10 80% by weight of propylene homopolymer in powder (ASTM D1238: 230 ° C., 2.16 kg) was blended, 0.5 parts by weight of antioxidant was mixed together with 100 parts by weight of this resin composition, and then melt mixed through a twin screw extruder to pelletize. . The melt index of this resin was 4.2 g / 10 min, and the properties and processing characteristics of the resin composition were evaluated by the above method.

[Comparative Example 4]

As confirmed by C-4 in Table 1, a biaxial extruder was mixed with 0.5 parts by weight of antioxidant against 100 parts by weight of propylene homopolymer having a melt index of 5.0 g / 10 minutes (ASTM D1238: 230 ° C., 2.16 kg). Pelletized by melt mixing through. The method and the processing characteristic of the resin composition were evaluated by the said method.

[Comparative Example 5]

As confirmed by C-5 in Table 1, melt index 0.25g / 10 in 70% by weight of the polymer of the long branch prepared above melt index 1.5g / 10 minutes (ASTM D1238: 230 ℃, 2.16kg) was introduced 30 wt% of propylene homopolymer in powder (ASTM D1238: 230 ° C., 2.16 kg) was blended, 0.5 parts by weight of antioxidant was mixed together with 100 parts by weight of the resin composition, and then melt mixed through a twin screw extruder to pelletize. It was. The method and the processing characteristic of the resin composition were evaluated by the said method.

Comparative Example 6

As can be seen from Table 1, the long branch prepared melt index 1.5 g / 10 min (ASTM D1238: 230 ° C., 2.16 kg) of the polymer prepared above was introduced through a twin screw extruder without mixing antioxidants. Pelletized. The melt index of this resin was 2.7 g / 10 minutes, and the characteristics and processing characteristics of the resin composition were evaluated by the above method.

As can be seen from the results of Table 1, Examples 1 to 5 in which the polymer having a long branch introduced were introduced, compared to Comparative Examples 2 and 4 using 100% by weight of propylene homopolymer, elastic strength, melt strength and thermal deflection characteristics. Was excellent.

Polymers with long branches that do not contain antioxidants (Comparative Example 6) have a very poor processing stability, resulting in an increased melt index and poor surface properties, but high melt strength and excellent vacuum properties. Indicated.

In blending a polymer having a long branch introduced with a propylene homopolymer having a melt index of 1.7 g / 10 min, the melt strength of Examples 1 to 3 in which the content of the long branch introduced propylene polymer is 30% by weight or more is longer than 100 mN. Compared to Comparative Example 1 in which the content of the propylene polymer in which the branch was introduced was 10% by weight, vacuum forming was excellent.

In elongational viscosity, point thickening appeared through the blending of polymers with long branches introduced, and the elastic force was 2.0 or more.

In blending with a propylene homopolymer having a melt index of 5.0 g / 10 min, especially when the content of the polymer having a long branch introduced was 50% by weight or more, it showed high melt strength and elasticity, and exhibited excellent vacuum formability.

Comparative Example 5 is a blend with a propylene homopolymer having a melt index of 0.25 g / 10 minutes, and the melt index is too low, so that the sheet forming is not possible due to a high load during sheet processing.

As can be seen through the examples and comparative examples, it can be seen that the resin composition according to the present invention greatly increases the thermal deflection phenomenon and the melt strength and improves the surface properties.                     

Therefore, according to the present invention, a highly elastic polypropylene resin composition suitable for use in a vacuum thermoforming process processed in a molten state can be effectively produced.

In addition, the polypropylene resin composition according to the present invention greatly improves the melt tension, and can be applied to existing impossible processes such as foaming process, vacuum molding process, and blow molding process. In addition, the polymer is introduced in the long branches used in the present invention is not produced by the method of crosslinking has the advantage that can maintain the properties of the thermoplastic resin as it is and can be recycled.

Claims (3)

The solid titanium catalyst for olefin polymerization is surface treated with a silane compound having two or more vinyl groups, followed by prepolymerization of the surface treated solid titanium catalyst with an olefin monomer and a diene compound to encapsulate a high molecular weight monomer around the catalyst. 30 to 95% by weight of a polyolefin polymer introduced with a long branch polymerized using a prepolymerization catalyst, and 5 to 70% by weight of a propylene homopolymer, and 0.05 to 0.5 parts by weight of an antioxidant based on 100 parts by weight of this resin composition. High elasticity polypropylene resin composition excellent in vacuum forming. According to claim 1, wherein the ratio of the melt index (ASTM D1238: 230 ℃, 2.16kg) of the polyolefin polymer (a) and the propylene homopolymer (b) in which the long branch is introduced (a / b) is 0.5 to 5.0 A highly elastic polypropylene resin composition having excellent vacuum formability. The high elastic polypropylene resin composition having excellent vacuum formability according to claim 1, wherein the high elastic polypropylene resin composition has a melt strength of 100 mN or more and an elastic force of 2.0 or more.