KR101007763B1 - Polypropylene resin composition for foam injection molding and foam produced using the same - Google Patents

Abstract

The present invention relates to a polypropylene resin composition for foam injection molding and a foam produced using the same, wherein the polypropylene resin composition of the present invention has a melt index of 3 to 50 g / 10 minutes and a molecular weight distribution (PI) of 7 or more. It is characterized by including a mixed resin and a blowing agent. When the foam is manufactured using the polypropylene resin composition according to the present invention, the foam cell density is controlled to provide a foam having excellent flexural strength, flexural modulus, and formability, and at the same injection conditions, weight reduction is achieved. The advantage is that it is possible.

Dialkoxy magnesium carrier, titanium catalyst, succinate internal electron donor, mixed phase resin, ethylene-propylene copolymer rubber

Description

Polypropylene resin composition for foaming injection molding and a foam prepared using the same}

The present invention relates to a polypropylene resin composition for foam injection molding and a foam produced by using the same, and more particularly, by including a propylene-based mixed phase resin prepared using a specific catalyst, The present invention relates to a polypropylene resin composition which is controlled and has flexural strength, flexural modulus, and the like, having moldability suitable for injection use, and a foam produced using the same.

Plastics commonly used in foam products are polystyrene resins and polyurethane resins. Since the resins are easy to control the foamability due to the high melt tension at the time of melting, the resins are used in a variety of ways from a soft buffer to a hard heat insulating material. However, the polystyrene resin has a disadvantage of poor heat resistance because the glass transition temperature is 100 ° C, and the polyurethane resin has a disadvantage in that secondary molding or recycling is not easy. In particular, the foam products produced by the plastics are limited in their use for injection products of automotive, electrical and electronic products because of their lack of mechanical rigidity.

On the other hand, polypropylene resin is excellent in mechanical properties and heat resistance, and can be widely used for injection products of automobiles, electrical and electronic products because it can be secondary molded and recycled. However, the polypropylene resin has a problem that can not catch the gas present in the resin during the foaming, due to the melt tension that sharply decreases after the melting point, the gas is ejected to the outside, or the foaming cell bursts to form large pores There is a disadvantage that the control of the foam is difficult.

For this reason, various methods have been proposed to increase the melt tension of polypropylene resins. The first is to irradiate linear polypropylene with electron beams to break up some main chains, and to combine the degraded main chains with other main chains to form long-chain branching with long side chains. However, there are problems in that installation and operation of expensive electron beam irradiation equipment is difficult, and productivity of reaction by irradiation is low, manufacturing cost is high, and commercialization is difficult. The second method is to introduce long chains by reacting organic peroxides with polypropylene under specific reaction conditions. However, in the post-treatment process, the production time extension, etc., the productivity is lowered because a batch reaction step is required. Third, there is a method of increasing melt tension by mixing a polyolefin resin having a very high molecular weight or a high side branch ratio with a linear polypropylene resin. However, this is hardly stiffness and heat resistance, there is a limit to the optimization by the mixing ratio. Fourth, there is a method of increasing the melt tension by crosslinking the polypropylene resin. However, since the gel is generated by the crosslinking reaction, there is a disadvantage that the marketability is poor.

The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is a propylene-based mixture having a wide molecular weight distribution prepared through the control in the polymerization step of the propylene-based resin using a specific catalyst It is an object to provide a polypropylene-based resin composition having a moldability suitable for injection use, and a foam produced using the same, by including a phase resin and controlling the foam cell density during foam injection molding.

The polypropylene resin composition according to the present invention has a melt index of 3 to 50 g / 10 minutes, and includes 0.1 to 10 parts by weight of a blowing agent based on 100 parts by weight of a propylene-based hetero phase resin having a molecular weight distribution (PI) of 7 or more. It features.

The propylene-based mixed phase resin used in the present invention is characterized in that it is polymerized in the presence of a catalyst prepared by reacting a titanium compound and a succinate internal electron donor with a dialkoxy magnesium carrier. More specifically, the propylene-based mixed phase resin is a series of at least two or more polymerization tanks in series in the presence of the catalyst component and optionally a catalyst system containing an organoaluminum compound and an external electron donor, in the preceding polymerization tank propylene alone After preparing the polymer portion, the product is transferred to a subsequent polymerization tank to copolymerize ethylene and propylene, whereby ethylene-propylene rubber (EPR) particles are finally dispersed in a matrix of propylene homopolymer and integrally It is prepared in a kneaded form.

In the process of producing the propylene mixed phase resin used in the present invention, the gas phase molar ratio of ethylene / propylene injected into the polymerization tank in the step of copolymerizing ethylene and propylene is preferably 0.15 to 0.25. When the ethylene / propylene gas phase molar ratio is less than 0.15, the ethylene content is low to lower the impact resistance of the resin, and when it exceeds 0.25, the propylene content is low to lower the rigidity of the resin.

In the propylene-based mixed phase resin, the average diameter of the ethylene-propylene copolymer rubber particles (average diameter is defined as the average value of the distribution values from the upper 15% and lower 15% removed from the diameter distribution measured in the region of 1cm × 1cm ) Is preferably in the range of 0.3 to 2.0 μm, but if it is outside the above range, the dispersibility of the propylene homopolymer, which is a matrix, is poor.

In the propylene mixed phase resin, the content of the ethylene-propylene copolymer rubber is preferably 5 to 20% by weight based on 100% by weight of the total propylene mixed phase resin, in terms of impact resistance and rigidity balance. .

The melt index of the propylene-based mixed phase resin used in the present invention is preferably 3 to 50 g / 10 minutes, but when the melt index is less than 3 g / 10 minutes, the melt viscosity is high, which is not preferable for injection molding, and is 50 g / 10 minutes. If it exceeds, the melt viscosity is low and the foaming rate is low, which is not preferable.

Molecular weight distribution (PI, Polydispersity Index) of the propylene-based mixed phase resin used in the present invention means a rheological molecular weight distribution index of dynamic shear shear rheology (Dynamic Shear Rheometry). The propylene-based mixed phase resin is polymerized using a catalyst prepared using a succinate internal electron donor, and thus has a molecular weight distribution (compared to the conventional resin polymerized using a catalyst prepared using a phthalate internal electron donor). PI) It has a broad molecular weight distribution of 7 or more. As the molecular weight distribution of the resin is wider, the higher the melt viscosity and the elongation strength, the higher the gas content in the cylinder contained in the molten resin by physical or chemical foaming action, It is effective to make the size of the generated micropores small and uniform. The molecular weight distribution of the propylene-based mixed phase resin may be quantified by Mw / Mn value of Gel Permeation Chromatography (GPC), in which case it is preferable that the Mw / Mn value of GPC is 10 or more.

The foaming agent included in the resin composition of the present invention is not particularly limited in kind, but may be used one or more selected from a chemical foaming agent and a physical foaming agent capable of foam molding during injection.

The chemical foaming agent is previously mixed with the resin, and then decomposed in a cylinder of an injection molding machine to generate gas such as carbon dioxide gas and nitrogen, preferably inorganic chemical foaming agent such as sodium bicarbonate, ammonium carbonate, or azodicarbon. Organic chemical foaming agents, such as amide and dinitrozopentatetramine, can be used, More preferably, inorganic chemical foaming agents with less decomposition residue, less odor at work, and easy to refine bubbles can be used. . In the inorganic chemical foaming agent, in order to stably and uniformly control bubbles of the foamed molded article, a foaming aid such as citric acid or inorganic fine particles such as talc may be added as a nucleating agent. In addition, when the inorganic chemical blowing agent is used, it is preferably used as a masterbatch in which 10 to 50 parts by weight of the blowing agent is mixed with 100 parts by weight of the polyolefin resin for handling, storage stability, and dispersibility during molding.

The physical foaming agent is a gaseous or supercritical fluid injected directly into the molten resin in the cylinder of the injection molding machine, and includes aliphatic hydrocarbons such as propane and butane; Cyclic hydrocarbons such as cyclobutane and cyclopentane; Organic gases such as halogenated hydrocarbons such as chlorodifluoromethane and dichloromethane, or inorganic gases such as nitrogen, carbon dioxide and air can be used.

In the polypropylene resin composition of the present invention, the amount of the blowing agent is preferably 0.1 to 10 parts by weight, but if it is less than 0.1 part by weight, it is not preferable because sufficient foaming effect is not expected. It is not preferable because it may adversely affect the strength and the like.

The polypropylene resin composition according to the present invention may further include a rubber filler and / or an inorganic filler.

The rubber filler is used to improve the impact strength, preferably an amorphous ethylene-alpha olefin copolymer or a styrene-olefin copolymer may be used, and more preferably an ethylene-alpha olefin copolymer may be used. . In the ethylene-alpha olefin copolymer, propylene, butene-1, hexane-1, octene-1, 4-methylpentene-1, heptene-1 and the like can be used, and the styrene-olefin air In the copolymerization, isoprene, butadiene, ethylene-propylene or the like can be used as the olefin. In the polypropylene resin composition of the present invention, the content of the rubber filler is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the propylene-based mixed phase resin, but when less than 0.1 parts by weight, the effect of improving the impact resistance by the rubber filler is low. It is not preferable, and when it exceeds 20 parts by weight, the rigidity is not preferable.

As the inorganic filler, preferably, one or more selected from the group consisting of talc, glass fiber, mica, mica, wollastonite, and clay may be used. In the polypropylene resin composition of the present invention, the content of the inorganic filler is preferably 0.5 to 30 parts by weight based on 100 parts by weight of the propylene-based mixed phase resin, and when less than 0.5 parts by weight, the physical properties and the foaming rate increase by the inorganic filler. The effect is not preferable because it is low, and when it exceeds 30 parts by weight, the rigidity is increased, but the impact resistance is sharply lowered, which is not preferable.

In the polypropylene resin composition according to the present invention, additives such as antioxidants, UV stabilizers, nucleating agents, pigments, flame retardants, antistatic agents, etc. may be used in combination with the above components, as necessary, within the range of not impairing the effects of the present invention. can do.

Foam according to the invention is characterized in that the polypropylene resin composition is prepared by the foam injection molding.

In the manufacture of the foam according to the invention, the foam injection molding is a general condition of polypropylene injection molding, injection temperature 170 ~ 250 ℃, mold temperature 10 ~ 100 ℃, injection speed 10 ~ 300mm / sec, injection pressure 10 It is performed under conditions such as ˜200 MPa. However, unlike the conventional injection molding machine, the foam injection molding machine has a shut-off nozzle for maintaining the gaseous pressure dissolved and dispersed in the cylinder and a gate valve for trapping the gas inside the mold ( The gate valve must be fitted. And for high foaming rate, a high injection speed is required to increase the pressure difference between the cylinder and the mold. Recently, in order to maximize the foaming rate in a mold, a core-back method of retracting and foaming a part of a mold after completion of injection is used, using a movable injection molding machine that can move a part of the mold forward and backward. I use it. The foam produced by the above-described method, the foamed layer is formed on the surface is beautiful in appearance, and the foam of high magnification made of uniform and fine foamed pores are generated inside, excellent in light weight and rigidity.

The foam of the present invention made from the polypropylene resin composition of the present invention has a beautiful appearance, preferably has a cell average size of 300 µm or less, and is excellent in physical properties such as flexural strength and flexural modulus, and is non-foaming under the same conditions. Compared to the weight reduction.

The polypropylene resin composition of the present invention has a moldability suitable for injection use by including a propylene-based mixed phase resin having a broad molecular weight distribution polymerized using a catalyst prepared using a succinate-based internal electron donor. Foam prepared from the composition is greatly improved in physical properties such as flexural strength, flexural modulus, and has the advantage that it can be reduced in weight. Therefore, the foam of the present invention can be variously applied to bumpers, door trims, instrument panels, etc., housings, covers, and frames of electric / electronic products.

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

≪ Examples and Comparative Examples &

The measurement / evaluation items of the overall physical properties in each Example and Comparative Example and the measuring method thereof are as follows.

Measurement method of resin and foam

The properties of the propylene-based mixed phase resins shown in Table 1 and the properties of the foams shown in Table 2 were measured as follows:

① Melt index (MI; g / 10 min) : measured under a load of 2.16 kg at 230 ° C. according to the method of ASTM D1238.

② Melt strength : Melt strength when resin melted at 200 ° C. leaves capillary rheometer using SMER (Samsung Melt Tension Rheometer) described in patent application No. 1999-0008553 and patent application No. 2001-0030112, etc. Was measured. At this time, the L / D of the plate was 16, the acceleration ratio was 1 mm / sec, and the chamber temperature was 140 ° C.

③ EPR (Xylene Extracted Content; Weight%) : The propylene-based mixed phase resin was dissolved in xylene for 1 hour at 140 ° C with 1% concentration, and then extracted after 2 hours at room temperature.

(4) T-C2 (mol%) : It is an ethylene fraction with respect to the whole resin composition.

⑤ Mw / Mn : Molecular weight distribution index using gel permeation chromatography.

⑥ Molecular weight distribution (PI, Polydispersity Index) : Storage rate where storage rate (Storage Modulus (G ')) and reduction rate (Loss Modulus (G ") meet using dynamic shear shear rheometry Molecular weight distribution index defined as the inverse of the value multiplied by 10 ⁶ (dynes / cm ² ).

⑦ foaming ratio : The foaming ratio was calculated through the resin weight ratio before and after foaming.

⑧ Average cell size (D ₈₀ , mm) : The size of the cells in the 100mm x 100mm of the foam was measured by an electron scanning microscope, the average diameter of the range except both sides in the size distribution chart was calculated.

⑨ Tensile strength (kg / ㎠) : measured according to ASTM D790 method.

Flexural strength and flexural modulus (kg / cm 2) were measured according to the ASTM D790 method.

IZ Izod impact strength at room temperature (kgf / cm) : measured at room temperature (23 ℃) according to ASTM D256.

Physical properties of the propylene-based mixed phase resins used in Examples and Comparative Examples are shown in Table 1 below.

Propylene Mixture Resin E / P
Weather Melt index
(g / 10 min) Melt strength
(mN) EPR
(wt%) T-C2
(mol%) Mw / Mn
(GPC) PI inside
Electron donor A 0.2 10 80 10 10 12 9 Succinate B 0.2 10 40 11 11 8 4 Phthalate C 0.1 10 85 4 6 11 8 Succinate D 0.3 10 65 21 25 10 9 Succinate

Using the resin of Table 1 to prepare a polypropylene resin composition according to the composition shown in Table 2, the resin composition was foamed under the conditions of injection temperature 200 ℃, mold temperature 100 ℃, injection speed 250mm / sec, injection pressure 200MPa Injection molded to prepare a foam. The physical properties of the prepared foams were measured and shown in Table 2.

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Propylene Mixture Resin
(Parts by weight)
A A A A A A B C D 100 100 100 100 100 100 100 100 100 Blowing agent ¹⁾
(Parts by weight)
2 2 2 2 2 2 2 2 2 Talc
(Parts by weight)
- 4 30 - 20 - - - - Fiberglass
(Parts by weight)
- - - 30 - - - - - EOR ²⁾
(Parts by weight)
- - - - 10 20 - - - Expansion ratio
(%)
10 9 10 9 11 11 8 9 10 Average cell size
(D ₈₀ , mm)
160 180 210 200 230 210 340 190 180 The tensile strength
(kgf / cm ² )
380 270 280 680 280 250 280 380 330 Flexural strength
(kgf / cm ² )
400 460 460 550 450 330 280 460 320 Flexural modulus
(kgf / cm ² )
18,000 19,000 28,000 37,000 22,000 16,000 11,000 19,000 13,000 IZOD (room temperature)
(kgfcm / cm)
6 4.5 4 4.5 32 65 5 2.5 6

Note: 1) Sodium bicarbonate

    2) ethylene-octene rubber

It can be seen that the foam of the embodiment prepared from the resin composition including the propylene mixed phase resin polymerized using a catalyst using a succinate-based internal electron donor has excellent foaming ratio, cell size, and mechanical properties. On the contrary, it can be seen that the foam of Comparative Example 1 made of a resin composition containing a propylene mixed phase resin polymerized using a catalyst using a phthalate-based internal electron donor is significantly inferior in flexural strength and flexural modulus. This is presumably because carbon dioxide generated by the blowing agent did not form pores independently in the resin due to the low strength of the molten resin, and the cell size was not controlled by forming large pores by releasing to the outside or bonding to each other. . In addition, the foam of Comparative Example 2 prepared from a resin composition containing a propylene mixed phase resin polymerized with an E / P gas phase molar ratio of 0.1 was significantly inferior in impact resistance, and the propylene mixed phase resin polymerized with an E / P gas phase molar ratio of 0.3 was used. It can be seen that the foam of Comparative Example 3 made of a resin composition containing significantly inferior in flexural strength and flexural modulus.

Claims (7)

Ethylene-propylene copolymer rubber particles having an average diameter of 0.3 to 2.0 µm dispersed in a propylene homopolymer. A propylene-based mixed phase resin having a melt index of 3 to 50 g / 10 minutes and a molecular weight distribution (PI) of 7 or more. Polypropylene resin composition containing 0.1-10 weight part of foaming agents with respect to 100 weight part. According to claim 1, wherein the propylene-based mixed phase resin is polymerized in the presence of a catalyst prepared by reacting a titanium compound and a succinate-based internal electron donor to a dialkoxy magnesium carrier, the ethylene in the propylene-based mixed phase resin The propylene copolymer rubber is produced by injecting ethylene and propylene in a gas phase molar ratio of ethylene / propylene of 0.15 to 0.25 to polymerize them. delete The polypropylene resin composition according to claim 1, wherein the polypropylene resin composition further comprises 0.1 to 20 parts by weight of a rubber filler and 0.5 to 30 parts by weight of an inorganic filler, based on 100 parts by weight of the propylene-based mixed phase resin. The polypropylene resin according to claim 4, wherein the rubber filler is an ethylene-alpha olefin copolymer rubber, and the inorganic filler is at least one member selected from the group consisting of talc, glass fiber, mica, wollastonite, and clay. Composition. The method of claim 1, wherein the blowing agent is a physical foaming agent selected from the group consisting of aliphatic hydrocarbons, cyclic hydrocarbons, halogenated hydrocarbons, nitrogen, carbon dioxide and air; Inorganic chemical foaming agents selected from the group consisting of sodium bicarbonate and ammonium carbonate; And an organic chemical foaming agent selected from the group consisting of azodicarbonamide and dinitrozopentatetetramine. A foam made from the polypropylene resin composition according to any one of claims 1 or 2 or 4 to 6.