KR20050057757A - Polypropylene resin composition and foam produced using the same - Google Patents

Abstract

The present invention is a resin composition prepared by melting and mixing 100 parts by weight of polypropylene having a long branch and a melt strength of 200 mN or more, 0.1 to 1.0 parts by weight of antioxidant, 1 to 20 parts by weight of foaming agent and 0.05 to 2.0 parts by weight of foaming nucleating agent, and The present invention relates to a foam prepared by extrusion foaming a resin composition. The polypropylene resin composition in which the long branch of the present invention is introduced has a melt tension of at least four times higher than that of a conventional resin, and a point aging phenomenon occurs when the elongation viscosity is measured. Not only is it excellent, but it is also recyclable.

Description

Polypropylene resin composition and foam produced using the same {Polypropylene resin COMPOSITION AND FOAM PRODUCED USING THE SAME}

The present invention relates to a resin composition comprising a polypropylene having a long branch introduced with excellent foamability, and a foam prepared by using the same. More specifically, a high molecular weight monomer is encapsulated around an optimum catalyst for alpha olefin polymerization. The present invention relates to a resin composition comprising polypropylene having a long branch introduced therein and a foam produced by extruding and foaming the resin composition.

In general, plastics used in foamed products include polyurethanes, polyolefins, PVC, ABS resins, urea resins, phenol resins, and the like, of which polystyrene and polyurethane are widely used.

Polystyrene has high elastic modulus, has high thermal insulation and cushioning properties, and is capable of foaming molding at high magnification, which enables to form lightweight foams, and is widely applied to food containers and the like because independent bubbles are formed.

Polyurethane has the advantage of producing a variety of foams through the selection of monomers, mainly soft foam is excellent in the touch is used for buffers, etc., the rigid foam is used as a building insulation.

As such, polystyrene and polyurethane have excellent properties as foaming materials, but are difficult to apply to specific applications for the following reasons. That is, polystyrene has very low oil resistance, so it is difficult to apply when the temperature is over 100 ℃ or contact with oil. Also, polyurethane is difficult to be used for food containers because it is difficult to be secondary molded or recycled after foam molding. Falls.

 Polypropylene, on the other hand, has a high balance of mechanical properties and excellent oil and heat resistance. In addition, since secondary molding and recycling are possible, it is used in a wide range of fields such as automobile parts, films, and injection molded products. However, polypropylene did not have satisfactory formability compared to other plastics due to the weak melt tension due to the linear chain structure.

 For this reason, various methods for increasing the melt tension of polypropylene have been proposed.

The first is a method of introducing long chain branches into polyolefins, which reduces the attractive force between the polymer chains in the processing process to give easy flow characteristics, and the molding process (particularly large blows). It is a method of showing high elasticity by making long branches form physical crosslinks with adjacent chains). As a specific method for obtaining a high elastic polyolefin by introducing long branches as described above, radicals are mainly formed on the polyolefins that have passed through the polymerization reactor through an electron beam or a reaction extrusion method, and reacted again to form long branches in the chain polyolefin. There is a way to.

The second method is to physically blend polyethylene into polypropylene with a low melt index. However, this method has a problem of low workability due to low melt index. Therefore, if a polymerization method and a blending method are developed to directly improve the elasticity by directly polymerizing a polyolefin having high elasticity, which is useful as a molding material, as a molding material, It is expected to expand the use of polyolefin.

The present invention has been made to solve the above problems, and an object thereof is to provide a polypropylene resin composition having excellent heat resistance and oil resistance by increasing melt tension and a foam prepared therefrom.

The resin composition of the present invention is characterized in that the long branches are introduced and comprises 100 parts by weight of polypropylene having a melt strength of 200 mN or more, 0.1 to 1.0 parts by weight of antioxidant, 1 to 20 parts by weight of blowing agent and 0.05 to 2.0 parts by weight of foaming nucleating agent. do.

The polypropylene polymer having such 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, and used for its preparation. Preferred examples of the catalyst component are described in Korean Patent Application No. 2001-0085640 filed by the applicant. In summary, the catalyst component is treated by subjecting the solid titanium catalyst for olefin polymerization to a silane compound having two or more vinyl groups and then prepolymerizing the surface treated solid titanium catalyst with an olefin monomer and a diene compound. It is a catalyst for alpha olefin polymerization, which is prepared by encapsulating a high molecular weight monomer around.

It is preferable that the melt index of the polypropylene polymer into which the long branch used for this invention was introduce | transduced is 0.1-10 g / 10 minutes (230 degreeC), and it is more preferable that it is 0.3-3.0 g / 10 minutes (230 degreeC). If the melt index is less than 0.1 g / 10 min, it takes a lot of load during processing and is accompanied by a rapid pressure rise. If the melt index is 10 or more, it is difficult to form a cell of the foam during foaming with a decrease in melt strength, and thus the open cell is opened.

In addition, the polypropylene polymer having a long branch used in the present invention has a strain rate greater than or equal to a certain value when measuring the draw viscosity, so that an extension hardening phenomenon occurs and the draw viscosity value is larger than that of the linear curve. It is characterized by growing.

To the polypropylene resin composition of the present invention, a known antioxidant known to be generally used in this kind of composition is added. The amount is preferably 0.1 to 1.0 parts by weight, and 0.3 to 100 parts by weight of polypropylene having long branches. 0.7 weight part is more preferable. If it is less than 0.1 part by weight, the antioxidant effect may be insufficient, and if it is more than 1.0 part by weight, the antioxidant effect reaches a certain level and does not increase any more.

In addition, the polypropylene resin composition into which the long branch of the present invention is introduced includes a conventional blowing agent and a foaming nucleating agent.

As the blowing agent, aliphatic hydrocarbons such as butane, isobutane, pentane, hexane and heptane; Alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; And at least one organic gas selected from the group consisting of halogenated hydrocarbons such as chlorodifluoromethane, dichloromethane, dichlorofluoromethane, trichlorofluoromethane, chloroethane, dichlorotrifluoroethane and perfluorocyclobutane. And / or one or more selected from the group consisting of inorganic gases such as carbon dioxide, nitrogen and air. The addition amount of the blowing agent is selected by the kind of blowing agent and the target foaming ratio, but in general, it is preferably 1 to 20 parts by weight, more preferably 5 to 10 parts by weight based on 100 parts by weight of the polypropylene into which the long branch is introduced. If it is less than 1 part by weight, there is a fear that the foaming effect is insufficient, and if it exceeds 1.0 part by weight, the foaming effect reaches a certain level and no longer increases.

In addition, the foamed nucleus may be a known one without particular limitation, but preferably a talc nucleating agent may be used. It is preferable that the addition amount of the foaming nucleating agent is 0.5 to 2.0 parts by weight based on 100 parts by weight of polypropylene having a long branch introduced, and when the content is less than 0.5 parts by weight, it is difficult to obtain a sufficient cell density. Is not expressed.

The composition of the present invention may also be added with other additives known to be generally used in this class of compositions.

There is no particular limitation in the method for producing the foam of the present invention, using a universally known tandem extruder, single screw extruder and twin screw extruder, etc., by mixing each of the above components under high temperature, high pressure conditions, and then extruded The manufacturing method can be selected.

The foam of the present invention prepared as described above has a foaming ratio of 20 to 40 times or more, wherein the cell density of the foam is 1.0E + 05 cells / cm ³ or more.

The present invention can be understood in more detail by the following examples, the following examples are merely examples for illustrating the present invention and do not limit the protection scope of the present invention.

EXAMPLE

The measuring method of the physical property in each Example and a comparative example is as follows.

Melt Index Measurement

It measured at 230 degreeC and 2.16 kg based on ASTMD1238.

Melt strength and draw viscosity measurement

Melt strength at 140 ° C. chamber temperature with respect to strands coming out through a plate of capillary rheometer at 200 ° C. using SMER (Samsung Melt Tension Rheometer) described in Patent Application Nos. 1999-0008553 and 2001-0030112, etc. The draw viscosity was measured. At this time, the plate had an L / D of 16 and an acceleration ratio of 1 mm / sec.

Expansion ratio

The density of the foam was measured by the weight of the foam and the volume determined by the water-immersion method, and the foaming ratio was calculated through the ratio of the resin density before foaming.

Cell density of foam

The number of cells per unit cubic centimeter of the foamed resin was measured, and the number of cells present in 100 x 100 µm of the foam was measured by a scanning electron microscope, and the following formula was calculated.

Cell density = (number of cells) ^3/2 × expansion ratio

 Example 1

A poly branch with a long branch with a melt index of 1.5 g / 10 min and a melt strength of 200 mN according to ASTM D1285 standard at 230 ° C., 2.16 kg, manufactured by the polypropylene manufacturing method described in Patent Application No. 2001-0085640. To 100 parts by weight of propylene, 0.5 parts by weight of antioxidant were mixed together and then pelletized by melt mixing through a twin screw extruder. Using this pellet, the melt index and melt strength were measured by the above method, and the results are shown in Table 1 below. Measurement results of the drawing viscosity using the SMER equipment is shown in FIG.

The resin pellets were supplied with 20 parts by weight of talc to 0.5 mm by weight of talc as a foaming nucleating agent in a 25 mm tandem extruder at 20 kg / h, and plasticized at 220 ° C. in a first stage extruder, and then n-butane was used as a blowing agent with respect to 100 parts by weight of the resin. 10 parts by weight was pressed and then quantitatively fed to the second stage extruder through a gear pump. After setting the temperature of the 40 mm second stage extruder to 180 ° C., the foamed strand was obtained while cooling the temperature of the static mixer and the die from 180 to 130 ° C. The foaming ratio and foam cell density of the foam thus prepared were measured as described above, and the results are shown in FIGS. 2 and 3, respectively.

Example 2

After pelletizing in the same manner as in Example 1, foam was prepared in the same manner as in Example 1 except that 0.8 parts by weight of talc was fed together with the foaming nucleating agent in the first stage extruder, and then the foaming ratio and the cell density of the foam were measured. It measured and the result is shown in FIG. 2 and FIG. 3, respectively.

Comparative Example 1

Except for using 0.5 parts by weight of antioxidant in 100 parts by weight of propylene homopolymer having a melt index ratio of 1.7 g / 10 minutes, pelletized in the same manner as in Example 1 to measure the melt index, melt strength, and elongation viscosity. 1 and FIG. 1. After the foam was prepared in the same manner as in Example 1 using the pellet, the foaming ratio and the foam cell density were measured, and the results are shown in FIGS. 2 and 3, respectively.

Example 1 Example 2 Comparative Example 1 Melt Index (g / 10min) 1.5 1.5 1.7 Melt strength (mN) 200 200 40 Thickening phenomenon Expression Expression Not manifested

As can be seen from the results of the above Examples and Comparative Examples (Table 1, Figures 1 to 3), the polypropylene resin composition in which the long branch of the present invention is introduced, the melt strength is superior to that of the existing resin foam ratio of the foam And excellent foam cell density, not only to expand the processing window that can produce high magnification foam in the foaming process, but also to maintain the properties of the thermoplastic resin as it is not a conventional crosslinking method, and can be recycled. Has the advantage.

1 is a result of measuring the elongation viscosity of the resin compositions of Examples and Comparative Examples,

Figure 2 shows the expansion ratio of the foam of the Examples and Comparative Examples,

Figure 3 shows the cell density of the foams of the examples and comparative examples.

Claims (6)

 A resin composition comprising a long branch is introduced and comprises 100 parts by weight of polypropylene having a melt strength of 200 mN or more, 0.1 to 1.0 parts by weight of antioxidant, 0.05 to 2.0 parts by weight of foaming nucleating agent and 1 to 20 parts by weight of blowing agent. The resin composition according to claim 1, wherein the polypropylene into which the long branch is introduced has a melt index of 0.1 to 10 g / 10 minutes (230 ° C). The resin composition according to claim 1, wherein the polypropylene into which the long branch is introduced has a melt index of 0.3 to 3.0 g / 10 minutes (230 ° C). The resin composition according to any one of claims 1 to 3, wherein the point severity phenomenon is expressed upon measurement of the elongation viscosity of the polypropylene into which the long branch is introduced. Foam formed by extrusion foaming the resin composition of any one of claims 1 to 4. The foam according to claim 5, wherein the foam has a foam ratio of 20 times or more, and the cell density of the foam is 1.0E + 05 cells / cm ³ or more.