KR20230073829A - Polypropylene resin composition for thin wall injection molding with excellent flowability and mechanical strength - Google Patents

Abstract

Disclosed is a polypropylene resin composition for thin film injection molded products that satisfies the balance of physical properties required in the art by maintaining mechanical strength such as excellent stiffness and impact strength while having high flowability in favor of thin film injection molding. The present invention is a) 86 to 94 parts by weight of a propylene block copolymer having a melt index (ASTM D1238, 230 ° C, 2.16 kg load) of 50 to 90 g / 10 min and an intrinsic viscosity ratio of 1.1 to 10 according to Equation 1 below; (b) 6 to 14 parts by weight of a high density polyethylene having a density of 0.955 to 0.965 g/cm 3 and a weight average molecular weight (Mw) of 110,000 to 170,000 g/mol; and (c) 0.06 to 1 part by weight of a nucleating agent.
[Equation 1]
Intrinsic viscosity ratio = (viscosity measured according to ISO 16014 standard for a 135 ° C trichlorobenzene (TCB) solution of solvent soluble in 150 ° C xylene solvent of propylene block copolymer) / (150 ° C xylene of propylene block copolymer) Viscosity measured according to the ISO 16014 standard for a 135°C trichlorobenzene (TCB) solution of the solvent insoluble content in a rene solvent).

Description

Polypropylene resin composition for thin wall injection molding with excellent flowability and mechanical strength}

The present invention relates to a polypropylene resin composition for thin-film injection-molded articles, and more particularly, to a polypropylene resin composition for thin-film injection-molded articles with excellent flowability and mechanical strength.

Polypropylene is a thermoplastic resin that is used for various purposes because of its excellent physical properties and low price. Depending on the physical properties required for each application, propylene homopolymer, propylene-ethylene random copolymer, or ethylene-propylene block copolymer (a propylene homopolymerized portion and an ethylene-propylene copolymerized portion (EPR) polymerized stepwise in a reactor) are produced. can be manufactured and used. For example, the propylene-ethylene random copolymer has excellent transparency and is mainly used for materials for household goods, and the ethylene-propylene block copolymer has excellent impact resistance and is mainly used for industrial materials.

In general, there are several methods for additionally expressing mechanical properties in polypropylene. Among them, when a modifier is blended with polypropylene, physical properties can be expressed relatively easily. For example, blending polypropylene with polyethylene or various types of elastomers is effective in improving impact properties. Accordingly, it is possible to increase the utilization of polypropylene through these technologies.

On the other hand, the market share of high-speed and thin-film injection molded products is increasing year by year due to consumer demand for superior design and convenient packaging solutions and regulations to reduce plastic consumption in many countries. In particular, the market growth rate in the packaging field is very fast, and mold technologies (multi-cavities, hot runners, etc.) for high-speed and thin wall injection molding (TWIM) optimized for packaging are also rapidly developing. Advantages of the TWIM technology include reduced cooling time due to thinner wall thickness, increased productivity due to a shorter molding cycle, reduced material cost due to a lighter product weight, and more products in the same volume. It can be stacked to reduce storage and transportation costs, and it is eco-friendly because plastic usage and carbon emissions are relatively reduced.

Since this TWIM technology requires rapid molding of thin products, high-flowability polypropylene with a very elaborately designed physical property balance between high flowability, stiffness and impact strength is required to make high-quality TWIM products. However, when the melt index (MI) of polypropylene is increased to improve flowability, there is a disadvantage in that physical properties are deteriorated due to low molecular weight, and in the case of propylene block copolymers, the ethylene content of ethylene propylene rubber (EPR), etc. Physical properties can be adjusted by changing the composition, but impact strength and rigidity have a trade-off relationship with each other, so there is a limit to physical property control. In addition, when making polypropylene composites by adding rubber or inorganic fillers to improve impact strength and stiffness in applications such as automobiles and home appliances, the effect of improving physical properties can be obtained, but the cost increases due to the additional compound process and materials. .

In European Patent Publication No. 1312617, US Patent No. 6610792, and US Patent No. 6723829, a low fluidity and high crystalline ethylene-propylene block copolymer is prepared, and then an organic peroxide is added to artificially form a polypropylene chain. ) by cutting the molecular weight to improve the flowability of the resin, but this method has problems in that workability is lowered due to a narrow molecular weight distribution, and odor and poor paintability occur.

Korean Patent Registration No. 1133359 discloses polypropylene having high fluidity and mechanical strength without artificially adding organic peroxide after preparing an ethylene-propylene block copolymer, but impact strength and stiffness are trade-off with each other. off), there is a limit to improving physical properties with polypropylene alone.

The present invention provides a polypropylene resin composition for thin-film injection molding that satisfies the balance of physical properties required in the art by maintaining mechanical strength such as excellent stiffness and impact strength while having high flowability in favor of thin-film injection molding. want to do

In order to solve the above problems, the present invention, (a) a propylene block having a melt index (ASTM D1238, 230 ° C, 2.16 kg load) of 50 to 90 g / 10 min, and an intrinsic viscosity ratio of 1.1 to 10 according to Equation 1 below 86 to 94 parts by weight of the copolymer; (b) 6 to 14 parts by weight of a high density polyethylene having a density of 0.955 to 0.965 g/cm 3 and a weight average molecular weight (Mw) of 110,000 to 170,000 g/mol; and (c) 0.06 to 1 part by weight of a nucleating agent.

[Equation 1]

Intrinsic viscosity ratio = (viscosity measured according to ISO 16014 standard for a 135 ° C trichlorobenzene (TCB) solution of solvent soluble in 150 ° C xylene solvent of propylene block copolymer) / (150 ° C xylene of propylene block copolymer) Viscosity measured according to the ISO 16014 standard for a 135°C trichlorobenzene (TCB) solution of the solvent insoluble content in a rene solvent).

In addition, the (a) propylene block copolymer is a propylene-ethylene random copolymer containing 1 to 9% by weight of ethylene, 75 to 90% by weight of propylene and 10 to 25% by weight of α with 2 to 10 carbon atoms other than propylene -Provides a polypropylene resin composition for thin-film injection-molded articles characterized in that a copolymer of olefin forms a block.

In addition, the (c) nucleating agent provides a polypropylene resin composition for thin-film injection-molded articles, characterized in that a mixture containing a fatty acid salt, a benzoate and a dioxaphosphocin salt.

In addition, the resin composition has a spiral flow measured according to the following method of 65 to 100 cm, a flexural modulus of 15,000 to 20,000 kgf/cm 2 , and an Izod impact strength of 7 to 10 kgf cm/cm. Provided is a polypropylene resin composition for thin film injection molded articles.

[Method of measuring spiral flow]

Spiral flow of the specimen after injection molding in a spiral mold with a width of 15 mm and a thickness of 1 mm under the conditions of a melt temperature of 200 °C, a mold temperature of 60 °C, an injection pressure of 60 bar, and an injection speed of 40 mm/s. flow) to measure the length.

[Method of measuring flexural modulus]

Measured by fixing the span of the specimen (127×12.7×6.4 mm) at 100 mm and applying a bending load at a rate of 28 mm/min according to ASTM D790 standard.

[Izod impact strength measurement method]

Measured notched impact strength of 1/8" specimen at room temperature (23℃) according to ASTM D256.

According to the present invention, a polypropylene resin composition having high flowability and maintaining mechanical strength such as excellent stiffness and impact strength can be provided through a combination of a specific composition of a propylene block copolymer, high-density polyethylene, and a nucleating agent. Through this, it can be used very suitably for the manufacture of thin-film injection-molded products that need to maintain mechanical strength while reducing the thickness of the product.

Hereinafter, the present invention will be described in detail through preferred embodiments. Prior to this, the terms or words used in this specification and claims should not be construed as being limited to the usual or dictionary meaning, and the inventor appropriately uses the concept of the term in order to explain his/her invention in the best way. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical spirit of the present invention. Therefore, since the configurations of the embodiments described in this specification are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, various equivalents and modifications that can replace them at the time of this application It should be understood that there may be

In a polypropylene resin composition for thin-film injection molded products, the present inventors have a propylene block air having specific flowability and viscosity characteristics in a situation where a highly fluidity polypropylene with a very elaborately designed physical property balance between high flowability, stiffness, and impact strength is required. It was confirmed that, when combining a high-density polyethylene having a specific molecular weight characteristic and a nucleating agent in a specific composition, it maintains mechanical strength such as excellent rigidity and impact strength while having high flowability, leading to the present invention.

Therefore, the present invention is (a) 86 to 94 weight propylene block copolymers having a melt index (ASTM D1238, 230 ° C, 2.16 kg load) of 50 to 90 g / 10 min and an intrinsic viscosity ratio of 1.1 to 10 according to Equation 1 below wealth; (b) 6 to 14 parts by weight of a high density polyethylene having a density of 0.955 to 0.965 g/cm 3 and a weight average molecular weight (Mw) of 110,000 to 170,000 g/mol; and (c) 0.06 to 1 part by weight of a nucleating agent.

In the present invention, 'thin film injection molded product' refers to a product that is injection molded in the form of a cover of an article having a thin overall thickness, for example, a cover of ice cream contained in a container made of plastic, with a thickness of 0.1 to 5 mm, preferably 0.2 mm. means a molded article having a thickness of from 2 mm to 2 mm.

The (a) propylene block copolymer is a base resin of a polypropylene resin composition for thin-film injection-molded products, and when mixed with high-density polyethylene and a nucleating agent described later, compared to conventional polypropylene applied to thin-film injection-molded products, the physical property balance of flowability and mechanical strength was found to be advantageous for

From this point of view, the (a) propylene block copolymer is a propylene-ethylene random copolymer containing 1 to 9% by weight of ethylene, 75 to 90% by weight of propylene and 2 to 10 carbon atoms other than 10 to 25% by weight of propylene It is preferable that a copolymer of phosphorus α-olefin forms a block.

In the present invention, the (a) propylene block copolymer may be prepared by sequentially polymerizing in two or more consecutive reactors. The operating conditions of each reactor may be the same or different, and propylene and α-olefins having 2 to 10 carbon atoms including ethylene, a catalyst system, and hydrogen are continuously supplied to each reactor as polymerization reaction raw materials. It may be added to adjust physical properties.

The (a) propylene block copolymer is polymerized by adding propylene and 1 to 5% by weight of ethylene in the first reactor to polymerize the propylene-ethylene random copolymer, and then in the second reactor in succession Presence of the propylene-ethylene random copolymer It can be formed by adding a small amount of propylene and an α-olefin comonomer having 2 to 10 carbon atoms other than propylene.

The α-olefin comonomer having 2 to 10 carbon atoms may be, for example, ethylene, 1-butene, 1-hexene, 1-octene or the like, preferably ethylene or 1-butene.

The (a) propylene block copolymer has a melt index (ASTM D1238, 230 ° C, 2.16 kg load) of 50 to 90 g / 10 min, and an intrinsic viscosity ratio of 1.1 to 10 according to Equation 1 below, preferably a melt index (ASTM D1238, 230 ° C, 2.16 kg load) is 60 to 80 g / 10 min, the intrinsic viscosity ratio according to Equation 1 below may be 1.1 to 3, more preferably the intrinsic viscosity ratio may be 1.5 to 2.5 .

[Equation 1]

Intrinsic viscosity ratio = (viscosity measured according to ISO 16014 standard for a 135 ° C trichlorobenzene (TCB) solution of solvent soluble in 150 ° C xylene solvent of propylene block copolymer) / (150 ° C xylene of propylene block copolymer) Viscosity measured according to ISO 16014 standard for 135℃ trichlorobenzene (TCB) solution of solvent insoluble content in ren solvent)

Here, in (a) the propylene block copolymer, the dispersion of the propylene-α-olefin copolymer produced in the second reactor is the viscosity of the propylene-ethylene random copolymer matrix and the propylene-α-olefin copolymer produced in the first reactor Since it is caused by the difference, it is important that the intrinsic viscosity ratio represented by Equation 1 above satisfies a specific range. The solvent soluble component refers to a component that is soluble at 150 ° C using a xylene solvent for the propylene block copolymer, and the solvent insoluble component refers to a component that is not soluble at 150 ° C using a xylene solvent for the propylene block copolymer. refers to ingredients. Intrinsic viscosity of each component may be measured using a viscometer in a 135° C. trichlorobenzene solution for the components obtained using the xylene solvent. At this time, the solvent-soluble fraction can be regarded as corresponding to the propylene-α-olefin copolymer, and the solvent-insoluble fraction can be considered to correspond to the propylene-ethylene random copolymer.

When the melt index is less than 50 g/10 min, the flowability and strength of the resin composition is lowered, and when it exceeds 90 g/10 min, the impact strength of the resin composition is lowered. In addition, when the intrinsic viscosity ratio is less than 1.1, the mechanical strength is lowered, and when the intrinsic viscosity ratio is excessive, it is difficult to expect additional improvement in required physical properties.

The content of the propylene block copolymer (a) may be 86 to 94 parts by weight, preferably 87 to 93 parts by weight, more preferably 88 to 92 parts by weight, based on the relative content of all components. If the content is less than 86 parts by weight, the flowability and rigidity of the resin composition is reduced, and if it exceeds 94 parts by weight, impact strength is reduced.

The (b) high-density polyethylene is mixed with the (a) propylene block copolymer to serve to improve the physical property balance of impact strength and stiffness in a trade-off relationship. From this point of view, in the present invention, the density is 0.955 to 0.965 g/cm 3 and a weight average molecular weight (Mw) of 110,000 to 170,000 g/mol is employed, preferably having a density of 0.957 to 0.963 g/cm 3 and a weight average molecular weight (Mw) of 120,000 to 160,000 g/mol. mol, more preferably a density of 0.958 to 0.962 g/cm 3 , and a weight average molecular weight (Mw) may be 130,000 to 160,000 g/mol.

When the weight average molecular weight (Mw) of the (b) high-density polyethylene is less than 110,000 g/mol, mechanical strength of the resin composition decreases, and when it exceeds 170,000 g/mol, stiffness and flowability of the resin composition decrease.

The content of the high-density polyethylene (b) may be 6 to 14 parts by weight, preferably 7 to 13 parts by weight, and more preferably 8 to 12 parts by weight, based on the relative content of all components. When the content is less than 6 parts by weight, the impact strength of the resin composition is lowered, and when it exceeds 14 parts by weight, flowability and rigidity are lowered.

The (c) nucleating agent is to maximize the physical property balance required as a whole by preventing a decrease in rigidity as well as improving the transparency of the polypropylene resin composition for thin-film injection molded products according to the present invention. It has been confirmed that the required performance can be realized in the case of a nucleating agent consisting of a mixture containing a fatty acid salt, a benzoate salt and a dioxaphosphocin salt, but not limited thereto.

The fatty acid salt may be, for example, fatty acid lithium and fatty acid sodium, the benzoate may be, for example, sodium benzoate, and the dioxaphosphosine salt may be, for example, bis(2,4,8,10-tetra-tert- Butyl-6-hydroxy-12H-dibenzo[d,g][1,3,2]dioxaphosphosine-6-oxide) aluminum hydroxide salt. Here, the fatty acids constituting the fatty acid salt include, for example, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, and nonanoic acid Nonanoic acid, decanoic acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, palmitoleic acid , stearic acid, oleic acid, vaccenic acid, linolenic acid, eleostearic acid, arachidic acid, and the like, preferably It may be palmitic acid or stearic acid, more preferably stearic acid.

At this time, the composition of the nucleating agent including the fatty acid salt, benzoate and dioxaphosphosine salt is preferably 10 to 20% by weight of the fatty acid lithium, 10 to 20% by weight of the sodium fatty acid, and 20 to 30% by weight of the sodium benzoate The weight % and the dioxaphosphocin salt may be 40 to 50 parts by weight, and as a nucleating agent having such a composition, HPN-715 nucleating agent of Milliken may be used.

The content of the (c) nucleating agent may be 0.06 to 1 part by weight, preferably 0.06 to 0.14 parts by weight, more preferably 0.08 to 0.12 parts by weight, based on the relative contents of all components. If the content is less than 0.06 parts by weight, the stiffness of the resin composition is reduced, and if it exceeds 1 part by weight, it is difficult to expect further improvement in the required physical properties.

The polypropylene resin composition according to the present invention maintains mechanical strength such as excellent rigidity and impact strength while having high flowability. Specifically, the polypropylene resin composition according to the present invention has a spiral flow of 65 to 100 cm, a flexural modulus of 15,000 to 20,000 kgf/cm 2 and an Izod impact strength of 7 to 10 kgf cm/cm, measured according to the following method. can be cm.

[Method of measuring spiral flow]

Spiral flow of the specimen after injection molding in a spiral mold with a width of 15 mm and a thickness of 1 mm under the conditions of a melt temperature of 200 °C, a mold temperature of 60 °C, an injection pressure of 60 bar, and an injection speed of 40 mm/s. flow) to measure the length.

[Method of measuring flexural modulus]

Measured by fixing the span of the specimen (127×12.7×6.4 mm) at 100 mm and applying a bending load at a rate of 28 mm/min according to ASTM D790 standard.

[Izod impact strength measurement method]

Measured notched impact strength of 1/8" specimen at room temperature (23℃) according to ASTM D256.

In addition, in the preparation of the polypropylene resin composition for thin film injection molded articles of the present invention, one or more additives known in the art as other additives other than the above components, such as antioxidants, neutralizers, UV stabilizers, antistatic agents, etc., are further included. If necessary, a heat-resistant stabilizer, a weathering stabilizer, a lubricant, a slip agent, a flame retardant, a pigment, a dye, and the like may be further included within a range that does not significantly impair its properties. In this case, each additive may be included in the range of 0.01 to 1 part by weight based on 100 parts by weight of the polypropylene resin composition for thin film injection molded articles of the present invention.

The polypropylene resin composition for thin-film injection-molded articles according to the present invention may be prepared by a known method for preparing a general resin composition. That is, (a) propylene block copolymer, (b) high-density polyethylene, (c) nucleating agent and other additives may be simultaneously mixed and then melt-extruded in an extruder to produce a product having a desired shape. For example, first, the components are mixed in an appropriate amount. At this time, the mixing may be performed by arbitrarily selecting a mixing means widely known in the art, such as a tumbler mixer, a blending machine, a hopper, and the like. Thereafter, the uniformly mixed composition may be melt-extruded using a twin-screw extruder and molded into a pellet state to prepare a final resin composition.

Hereinafter, the present invention will be described in more detail through specific preparation examples, examples and comparative examples.

Preparation Example: Preparation of propylene block copolymer

In the first reactor, propylene and ethylene were introduced to polymerize the propylene-ethylene random copolymer, and then propylene and ethylene were additionally added together with a catalyst in the presence of the propylene-ethylene random copolymer in the second continuous reactor, so that each reactor A propylene block copolymer having the following specifications was prepared by adjusting operating conditions, monomers, catalysts, hydrogen supply, and the like.

The above-prepared propylene block copolymer, high-density polyethylene and nucleating agent of the following specifications were put into a twin-screw extruder having a screw length / diameter (L / D) ratio of 25 and a diameter of 40 mm with the composition shown in Table 1 below, and heated to 170 to 210 ° C. After melting and kneading under conditions, cooling and solidification was performed to prepare a pellet-shaped resin composition, and the pellet-shaped resin composition was molded at a temperature range of 180 to 240 ° C. using an injection molding machine to prepare a physical property specimen.

[Ingredient Specifications]

(A1) propylene block copolymer

Melt index (MI) 60 g/10min (230°C, 2.16 kg load), density 0.900 g/cm 3 , ethylene content 9% by weight, intrinsic viscosity ratio 2.2.

(A2) propylene block copolymer

Melt index (MI) 80 g/10min (230°C, 2.16 kg load), density 0.900 g/cm 3 , ethylene content 9% by weight, intrinsic viscosity ratio 2.2.

(A3) propylene block copolymer

Melt index (MI) 35 g/10min (230°C, 2.16 kg load), density 0.900 g/cm 3 , ethylene content 9% by weight, intrinsic viscosity ratio 2.2.

(A4) propylene block copolymer

Melt index (MI) 100 g/10min (230°C, 2.16 kg load), density 0.900 g/cm 3 , ethylene content 9% by weight, intrinsic viscosity ratio 2.2.

(A5) propylene block copolymer

Melt index (MI) 80 g/10min (230℃, 2.16 kg load), density 0.900 g/cm 3, ethylene content 9% by weight, intrinsic viscosity ratio 1.

(A6) propylene block copolymer

Melt index (MI) 80 g/10min (230°C, 2.16 kg load), density 0.900 g/cm 3 , ethylene content 9% by weight, intrinsic viscosity ratio 3.1.

(B1) high-density polyethylene

Melt index (MI) 2 g / 10 min (190 ° C, 2.16 kg load), weight average molecular weight (Mw) about 180,000 g / mol, density 0.959 g / cm 3. Below, the weight average molecular weight was measured by Polymer Laboratories' GPC.

(B2) high-density polyethylene

Melt index (MI) 5 g/10min (190° C., 2.16 kg load), weight average molecular weight (Mw) about 150,000 g/mol, density 0.959 g/cm 3 .

(B3) high-density polyethylene

Melt index (MI) 20 g/10min (190° C., 2.16 kg load), weight average molecular weight (Mw) about 100,000 g/mol, density 0.959 g/cm 3 .

(C) nucleating agent

Milliken's nucleating agent HPN-715 was used.

division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 propylene block copolymer
(parts by weight) A1 90 - - - - 100 - - A2 - 90 - 90 - - 100 - A3 - - - - 100 - - 90 A4 - - - - - - - - A5 - - - - - - - - A6 - - 90 - - - - - high density polyethylene
(parts by weight) B1 - - - - - - - - B2 10 10 10 10 0 0 0 10 B3 - - - - - - - - nucleating agent
(parts by weight) C 0.1 0.1 0.1 0.15 - - - 0.1 division Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Comparative Example 11 - propylene block copolymer
(parts by weight) A1 - - - - - - - A2 - - 95 85 90 90 90 A3 - - - - - - - A4 90 - - - - - - A5 - 90 - - - - - A6 - - - - - - - high density polyethylene
(parts by weight) B1 - - - - 10 - - B2 10 10 5 15 - - 10 B3 - - - - - 10 - nucleating agent
(parts by weight) C 0.1 0.1 0.1 0.1 0.1 0.1 0.05

Experimental example

In order to evaluate the physical properties of the prepared polypropylene resin composition, the specimens prepared according to Examples and Comparative Examples were left at 23 ° C. and 50% relative humidity for 24 hours or more, and then the physical properties were measured according to the following method, and the results are shown below. Table 2 shows.

[measurement method]

(1) Liquidity evaluation (spiral flow measurement)

Spiral flow of the specimen after injection molding in a spiral mold with a width of 15 mm and a thickness of 1 mm under the conditions of a melt temperature of 200 °C, a mold temperature of 60 °C, an injection pressure of 60 bar, and an injection speed of 40 mm/s. flow) length was measured.

[Method of measuring flexural modulus]

According to the ASTM D790 standard, the span of the specimen (127 × 12.7 × 6.4 mm) was fixed at 100 mm, and a bending load was applied at a rate of 28 mm/min.

[Izod impact strength measurement method]

According to ASTM D256, the notched impact strength of a 1/8" specimen was measured at room temperature (23°C).

division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Spiral Flow (cm) 65 71.1 70.5 70.4 59.7 67.4 73 54.3 Flexural modulus
(kgf/cm2) 15,800 16,200 15,200 16,300 12,900 13,000 13,500 15,000 Izod impact strength
(23℃, kgfcm/cm) 7.9 7.4 8.3 7.1 7.5 6 5 8.7 division Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Comparative Example 11 - Spiral Flow (cm) 78.7 72 72.3 66 68.4 73.2 70.8 Flexural modulus
(kgf/cm2) 16,400 15,900 16,500 14,900 14,900 15,400 14,200 Izod impact strength
(23℃, kgfcm/cm) 6.3 6.7 5.9 7.6 8.9 6.5 7.6

Referring to Table 2, according to the present invention, the polypropylene resin compositions (Examples 1 to 4) in which a propylene block copolymer having specific flowability and viscosity characteristics, a high-density polyethylene having specific molecular weight characteristics, and a nucleating agent are combined in a specific composition are It can be seen that the balance of physical properties is designed very elaborately by maintaining mechanical strength such as excellent stiffness and impact strength while having high flowability. However, when (a) the intrinsic viscosity ratio of the propylene block copolymer is relatively excessive (Example 3) and (c) the nucleating agent content is relatively excessive (Example 4), it is difficult to expect additional improvement in the required physical properties. Therefore, it is reasonable to apply it in the suggested composition.

On the other hand, if (b) high-density polyethylene and (c) nucleating agent are not added, (a) when the melt index of the propylene block copolymer is low (Comparative Example 1), the impact strength is high, but the flowability and stiffness are lowered, and appropriate melting In the index (Comparative Examples 2 and 3), it can be seen that the flowability is high, but the stiffness and impact strength are lowered.

In addition, even if (b) high-density polyethylene and (c) the nucleating agent are added, (a) when the melt index of the propylene block copolymer does not reach a certain level (Comparative Example 4), the flowability and stiffness are lowered, and the melt index is excessively high. In the case (Comparative Example 5), it can be seen that the impact strength is lowered.

In addition, (a) it can be seen that the mechanical strength is lowered when the intrinsic viscosity ratio of the propylene block copolymer does not reach a specific level (Comparative Example 6).

In addition, (b) it can be seen that when the content of high-density polyethylene does not reach a certain level (Comparative Example 7), the impact strength decreases, and when the content is excessive (Comparative Example 8), flowability and stiffness decrease.

In addition, (b) it can be seen that when the molecular weight of high-density polyethylene is excessively large (Comparative Example 9), stiffness and flowability decrease, and when the molecular weight does not reach a certain level (Comparative Example 10), mechanical strength decreases. .

In addition, (c) it can be seen that the stiffness decreases when the nucleating agent content does not reach a specific level (Comparative Example 11).

Above, preferred embodiments of the present invention have been described in detail. The description of the present invention is for illustrative purposes, and those skilled in the art will understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention.

Therefore, the scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning, scope and equivalent concept of the claims are included in the scope of the present invention. should be interpreted

Claims (4)

(a) 86 to 94 parts by weight of a propylene block copolymer having a melt index (ASTM D1238, 230 ° C, 2.16 kg load) of 50 to 90 g / 10 min and an intrinsic viscosity ratio of 1.1 to 10 according to Equation 1 below;
(b) 6 to 14 parts by weight of a high density polyethylene having a density of 0.955 to 0.965 g/cm 3 and a weight average molecular weight (Mw) of 110,000 to 170,000 g/mol; and
(c) 0.06 to 1 part by weight of a nucleating agent;
A polypropylene resin composition for thin-film injection molded articles comprising:
[Equation 1]
Intrinsic viscosity ratio = (viscosity measured according to ISO 16014 standard for a 135 ° C trichlorobenzene (TCB) solution of solvent soluble in 150 ° C xylene solvent of propylene block copolymer) / (150 ° C xylene of propylene block copolymer) Viscosity measured according to the ISO 16014 standard for a 135°C trichlorobenzene (TCB) solution of the solvent insoluble content in a rene solvent). According to claim 1,
The (a) propylene block copolymer is a propylene-ethylene random copolymer containing 1 to 9% by weight of ethylene, 75 to 90% by weight of propylene and 10 to 25% by weight of α- A polypropylene resin composition for thin-film injection molded articles, characterized in that an olefin copolymer forms a block. According to claim 1,
The (c) nucleating agent is a polypropylene resin composition for thin-film injection-molded articles, characterized in that a mixture containing a fatty acid salt, a benzoate and a dioxaphosphocin salt. According to claim 1,
The resin composition has a spiral flow measured according to the following method of 65 to 100 cm, a flexural modulus of 15,000 to 20,000 kgf / cm 2 , and an Izod impact strength of 7 to 10 kgf cm / cm A polypropylene resin composition for thin-film injection molded articles comprising:
[Method of measuring spiral flow]
Spiral flow of the specimen after injection molding in a spiral mold with a width of 15 mm and a thickness of 1 mm under the conditions of a melt temperature of 200 °C, a mold temperature of 60 °C, an injection pressure of 60 bar, and an injection speed of 40 mm/s. flow) to measure the length.
[Method of measuring flexural modulus]
Measured by fixing the span of the specimen (127×12.7×6.4 mm) at 100 mm and applying a bending load at a rate of 28 mm/min according to ASTM D790 standard.
[Izod impact strength measurement method]
Measured notched impact strength of 1/8" specimen at room temperature (23℃) according to ASTM D256.